Sounds like you had a radio problem. Did you happen to look at the lights on the O/I during this odd behavoir? (We actually dedicate one of our drive team as a status montior.) If your No Data/Radio light went Red, your robot would have appeared to 'died', simply because you don't have control anymore. There are a number of reasons for loss in Radio connection, some of which are unexplained (-shudder- Anapolis Regional 2006 (yeah, yeah, this is OCCRA, not FRC) ... I was on Team 181 paired with a couple of other awesome teams... what are the odds that TWO radios on the same alliance drop out during the same match for -no apparent reason-??), but this sounds like the most likely behavior.
Another possibility are a loose battery connection that got reconnected after you jostled the bot around when picking it up. Do you remember if the there was power to the bot when you went out to the field to retreive it?
My FRC 2 cents where it probably doesnt belong
,
Jacob