I'm sure someone will come up with the "actionless contest" argument but I don't think it applies here. That rule (NF 10-1-5) is called when a team delays and the other team cannot do anything about it. In this case, team A could have come and got the ball at any time (assuming there wasn't some "no backcourt guarding" rule in effect in this game like there is in some rec leagues).
In any case, the 10 second count was flat out wrong. There was never team control. To establish team control at a time when there is none, such as during a throwin, you must have player control established. To establish player control, a player must be holding or dribbling a live ball inbounds. This did not happen here, thus no player control, thus no team control, thus no legal 10 second count.
This wouldn't have been a problem if the clock was running, since it eventually would run out. But coming out of a timeout, there was no clock going.
What would I have done? Now that I've had time to think about it, I would have blown my whistle, called it inadvertant and made team B inbound again. If they did it again, I would do it again. I think eventually, someone would touch the ball inbounds.
Another option would be to blow the inadvertant whistle, make team B inbound again and claim B1 stepped over the line while inbounding, then give the ball to team A.
While none of these "solutions" may seem fair or within the letter or spirit of the rules, you gotta admit they're at least creative.
