...again your terminology is unclear...
but it sounds like your chain overshifted off the largest cog and wedged between the spokes and freewheel.
typically this occurs if the rear derailer limit screws are not set properly
or if the rear derailer has been misaligned via impact (not necesarially from a crash, can be as minor as someone at the bike racks next to you knocking it by accident)
I'd check those two things: derailer alignment and limit screws
If your LBS is good, they already checked that out when they did your repairs; and you should be fine now.