Here's a hint about this. There's about a 0% chance I'm putting 2 thumbs in the air if a partner asks me for help.

Guessing Game ???
 

And what if you were watching for an illegal screen your primary coverage area and didn't see the ball go out of bounds? Are you still not putting up two thumbs?

Yes, that's what he is saying. And that's what the camp observer was trying to convey also.

Remember, he is not telling YOU or ANYBODY ELSE what to do, he is saying what he would do.

That's what I'm saying.

Two Thumbs Up ...
 

This has definitely got to be a "When in Rome ..." thing. Two, or more, officials, who have absolutely no idea who last touched a ball, that subsequently goes out of bounds, with a rule in their pocket that allows them to remedy this situation with a held ball, and instead, an official mentally flips a coin?

Well, we pretty much do the same thing here with train wrecks. If we don't know to call a block, or a charge, we are told to guess, and then to sell the call.

Easy Call, For Everyone But ...
 

I've given this a little more thought. Let's say that it's not a difficult out of bounds call, it just that (in a two person game) both officials didn't see the play.

The lead, tableside, is closely watching a very physical matchup in the opposite tableside post position. The trail is closely watching some possible "ugly" illegal screens near the opposite tableside wing. A long pass is thrown from A1, unguarded, near the table, toward deep wing A2, also table side, who is guarded by B2. The pass misses all twenty fingers by an inch, and goes out of bounds on the lead's endline. Everybody in the gymnasium, including the two coaches, knows who caused the ball to go out of bounds except the two officials. Lead sounds his whistle, holds up his open hand to stop the clock, and looks to the trail for help. The trail, schooled by this camp observer, mentally flips a coin, loses the coin flip, and calls, and signals, A ball.

This just doesn't seem right, but like I said earlier, it's one of those "When in Rome ..." situations.

My answers always apply to 3-man unless otherwise noted. And as I do still go to camp, I understand the philosophy being espoused that, between 3 very competent officials, someone needs to know who last touched the basketball. It had to have happened in somebody's primary.

In your situation, a brief look at the players starting for the other end of the floor is all you need to make the call.

I just don't know how many times it can be said. There are clinicians who consider it poor officiating to NOT have a call amongst the crew (and that includes 2-man for many of them).

Hopefully with 3, someone will have a good look at the play. With 2, the odds are much less likely that, when the primary official gets thier line blocked, the other official will have a look at all.

If I'm the one asked for help, if I don't know anything I will give a subtle shrug or shake of the head. If I'm the one asking, and I get 0 help, if I have an educated guess based on player reaction or anything at all, I'll go with that. But if nobody has any idea at all, I see the arrow as the least of the evils. Having said that, I don't recall the last time I used the arrow in this situation.

This. The players will almost always give it away with their first step. If both teams start heading one way, you probably ought to point that way.