Can a speaker blow while it's turned off???? (coil blown). I've seen it happen twice but how?

Have a JBL eon 18" sub that has blown twice now without even being turned on. Sounds weird right?

First time was a couple of years ago. Went to turn it on and it was a zilch from the sound. Some rewinding was done of the memory but I was reasonably sure it had been working fine at the last gig and had been switched off as normal. Some blame was pointed at the person who was running it the loudest. Maybe it blew and we just didn't notice. We went to some effort and cost to order a new cone, reconed it which was kinda fun and got it working again.

However .... last week it happened again. Went to switch it on and zero. I'm 100% certain it was switched off while in a working condition at the last gig. That was a few months ago. It was transported by vehicle and then left in a shed. Definitely not dropped etc. Obviously won't bother reconing it this time.

How is this possible?