Similar thing happened to me... except it was in my cary bag, with about $800 worth of on-road RC equipment in the trunk of my car.
a 7 cell 3000mAh 8.4V NiMH battery pack with exposed battery ends(ran out of heat shrink) was up against one of my screw drivers...
Didn't notice until i pulled my bag out of the car and heard the last cell pop...
Bag and everything in it was covered in battery acid, and the trunk of my car stank for weeks....
After all that, i made the switch to Hard Case Li-Po packs.
5 years without a problem

a 7 cell 3000mAh 8.4V NiMH battery pack with exposed battery ends(ran out of heat shrink) was up against one of my screw drivers...
Didn't notice until i pulled my bag out of the car and heard the last cell pop...
Bag and everything in it was covered in battery acid, and the trunk of my car stank for weeks....
After all that, i made the switch to Hard Case Li-Po packs.
5 years without a problem

