I had a situation last week I've been going over in my head. Home coaches aren't happy, they end up losing by around 5 or so. T'd home coach with about 2 minutes left.
At half time, home assistant saw me sweating and gave me a towel on the way to the locker room. After the game, I'm waiting near the door for my partner to catch up so we can leave. Home AC comes to about 20 feet from me and asks,

"Where's that towel I gave you."
"It's in the dressing room, coach."
"Make sure you leave it. I don't trust you guys, for a number of reasons."

Thoughts in my head:
1) I should probably T that, but the games over, and I have to walk across the gym to do it.
2) Home HC is between me and the table, and giving this T is likely to result in a 2nd on the HC by the time it's over.
3) Let's get out of here.

I don't feel too bad about passing it up since the game was over, but at the same time I don't want coaches to feel like it's "open season" once the final buzzer sounds. I think the time could have been ripe for a short heart-to-heart with him, along the lines of, "Coach, I expect you think I missed some calls, and I may have missed a couple here and there. However, that doesn't give you the right to question my integrity in front of people like that."
But that's a much longer statement than I like to have with coaches.
Oh well, I'll let it go, I suppose. I just don't like that I let that go without comment.

"Thanks for the towel, coach. It was cottony soft."

It was obviously a jerk comment, but I'm pretty confident you can't whack him once you've left the court.

The obvious thing to do is nod and say thanks, then place his towel in the toilet and flush repeatedly, j/k.

It's amazing how many coaches think they are in a safe zone whenever that final horn goes off.

I wouldn't respond.

I wouldn't acknowledge his statement.

I would write it up in a report to my assignor.

"...and the horse you rode in on"

We were still on the court, otherwise I wouldn't even question my response. I just kind of looked at him and told him it would be there when we left.
In an uncomfortable twist, the two of them had to let us in the dressing room, since the varsity guys had popped into the other gym to catch the end of the other game. The AC (who I think was the HC's dad) said, as he was opening the door, "I want to say, from experience...."
I interupted him there, and told him I didn't want the conversation to continue since I couldn't see it going anywhere positive. The HC came in, and tried to make a point, and I repeated myself.
"What are you going to do, give me another technical?"
"No, coach. I'm just asking that we drop this conversation."
"Well, I don't think you were approachable in the game."
"Well, I explained every call you asked me to."
"Can I ask why I got the T?"
"Because I'd warned you already to stop."
Coach: "Well, good luck the rest of the season."

This is why I tried to get off the court and away from the coaches.

Sorry to vent, y'all.

It should be mandatory for schools to either provide us with a key to the dressing room or have some form of game management be responsible for letting us in/out of the changing area. Our mechanics are designed to prevent these types of exchanges and they do us no good if we now have to find the coach to open our room and invite the exchange. It doesn't help us and it certainly is hard on the coaches who are also trying to unwind from a competitive game. To me, it happens far too often.

The lad is wise beyond his years. This is, of course, the correct answer, with the possible addendum of cc'ing the report to the state athletic association.

Let me add a meaningless, but enthusiastic ME TOO to this.

For all the coaches and AD's out there: Provide someone with a towel and key to open the official's dressing room. I bet 90% of the places we go to, there is no one who does a thing for officials unless we ask. The 10% that do are the schools that we love to go work for. Common sense says you don't take people for granted. Try assigning someone to the officials and see how much better the atmosphere is.

I don't need a towel, but it would be nice if there was somsone to bring accompany us back to the lockeroom after halftime and end of the game. Most schools do this, so I am happy.

I don't need a towel either, but it's reeeeeeeally nice when we get one. It's just a little thing, but you don't have to carry a wet bulky towel home and it's just one little thing I appreciate a lot about college games.

Towel? Heck, I'd be happy if every school just had a bottle of water for you at half time. A drink of some kind is going to directly benefit the game (dehydration leads to muscle fatigue and poorer performance by the officials).

I think you handled the second part of the situation (in the locker room) correctly. The problem with our lower level games (Adam and I work in the same association) is that our game management in many cases is none other than the head coach of the home team. Not a situation we like, but with budgets and such, that's what we get. Where were at for this game?