Okay, something happened unexpected today and I was wondering if anyone out there can tell me exactly how?

After going to the pool, a pair of my sons spare shorts were left inside my van on top of a laundry bottle.  (It was Purex laundry detergent which is pictured below).

Photo By D. Wildermuth of Pro Market Me Inc.
I was at the pool for a few hours during the day… It was about 95 degrees outside so I would imagine it was significantly hotter inside the van.  When I left, I had to put some items in the back of my van.  I was in shock what I saw next.  Take a look at the picture of the shorts below.

Photo by D. Wildermuth of Pro Market Me Inc.
Photo by D. Wildermuth of Pro Market Me Inc.

The fabric on the shorts where it was on top of the laundry detergent bottle completely disintegrate.  Mind you this was a SEALED bottle of detergent.  How can an unopened bottle of laundry detergent eat away at this material?  The shorts were made of 100% cotton.  I would love to hear anyone who may know how this happened and the safety ramifications?  Thanks for reading