From your description, it sounds like it could be a staple on the roof caused a leak. The confusing part is the storage lot's involvement but maybe they play some part in the ongoing maintenance as part of the storage service.
Anyway, that's my guess!
Mike, Sue, Sissy and Little Man
2015 Ford F350 Lariat FX4 6.7 CC DRW
2015 Eagle Premier 351RSTS