Stad0902000

Had a scenario this week (adult softball to be clear), where an umpire started calling timeout, had hands raised to the point where multiple could see it, umpire also admitted to both teams that he started calling timeout. As he was doing this, runner from 3rd started to go home. Throw was made home and was called out on a close play at home. I was always under the impression that as soon as any indication of dead ball is started, a dead ball/timeout call needs to stand, similar to an inadvertent whistle in other sports, as there’s no way to know from that point on how players are effected by the umpire signal. I’ve been unable to find an actual rule touching on this though so was hoping to get some clarity here. Am I right in my assumption, or off base here? (Pun intended)