Propane tank locks for my TT

Years ago, I had a popup trailer stored in my son-in-laws barn. The barn burned to the ground taking our popup with it including the partially full propane tank on the tongue. The tank was blackened and a bit warped but did not explode.

Not sure why as we were in Florida for the winter when it happened and was not able to talk to the firemen about it. Just glad it didn't explode.:E. Posted a picture on RV.net shortly after it happened but the picture was lost during the Photobucket fiasco several years ago.
Barney