What if two teammates crash into each other and the official whistles and signals a foul only to then realize that no opposing player was involved?

I would absolutely reverse that call ... so I guess there are examples.

Up until 5-6 years ago in NFHS, an inadventent whistle resulted in the possession arrow. Perhaps the coach officiated in a time when this was the case (and he had the arrow).

I don't recall that being the rule (assuming there is TC at the time of the IW)

Nor do I????

Basically, anything can be changed after it is signaled unless it is conflicting judgements of the very same act (was it a block or a charge). Everything else is open for discussions. It may not be advisable, but it is at least an option.

Not only is it accepted but it is actually the rule. What matters is not what the official thought happened but what actually happened. If they blow the whistle and there was no violation, even if they thought there was one to start with, the rules grant the ball back to the team in control or the team that is still due a throwin/FT for a prior infarction....or a AP arrow if none of the above apply.

They could. I did it once. I was trail, partner lead at the baseline. He called a double dribble on a player at half court. The defender had knocked the ball out of the opponents hands after the dribble had ended, creating a new opportunity for a dribble which the offensive play made use of. He didn't see the defender knock the ball away and only knew that the offensive player had already dribbled. He refused to change the call and we talked about it after the game.
The foul call could be overturned if, by rule, it was at a time when a foul could not occur such as a common foul after the ball is dead.

Had one last night in a spring JV girls game: Double whistle, partner is signaling a travel while I have a fist up. We went with the foul as it happened first.

I've also had a partner whistle and signal a BC violation on a throwin play where the receiving player jumped from the FC to the BC and caught the ball in the air. As soon as he whistled it, he called me over to talk himself out of the call. He reversed it.

I've had two partners do this.

And Boy, Did I Feel Foolish ...
 

Been there. Done that. I believe twice in thirty-two years.

This and Cam's comment gave me pause. I believe I was thinking of double fouls, not inadvertent whistles. Sorry, my mistake.

In broader terms, a wise man changes his mind. You anticipate something, but something else happens, but you accidentally make the signal for what was anticipated. Tap yourself on the chest if you want, then make the correct signal. Or, if your partner made a call at the same time, you can drop you signal and walk away. It happens. There is nothing in any book which prevents it.

The Infamous Blarge Rears Its Angry Head ...
 

See 4.19.8 Situation C (Especially when one, or both, coaches see both signals). You're probably not going to be able to walk away, by rule, from this one.

It doesn't mean the same thing in his book as it does in everyone else's.

The case doesn't mention
signals but if it did what the coach saw or didn't see would not affect the call.

Smoke Signals ???
 

"One official calls a blocking foul on B1 and the other official calls a charging foul on A1"

Without signals, just exactly how are two officials going to "call" two different fouls? Without signals it would just be a race to the table to see who gets there, and makes the "call", first.