This was my biggest fear and I think it was because I was stuck in a very small elevator for 2.5 hours with 8 other squashed people. Sure I felt a little anxiety when we were in there but I am only realising now (6 years after the incident)I was fine until I looked back and thought all the negatives.
"What if" thoughts are sooooo negative. All the time I was thinking "What if I get stuck again". What you are subconsciously doing is SCARING YOURSELF.. Change the What if thoughts to "So what if" thoughts..
So what if I get stuck in an elevator, SO-What !!

.... Yes, you may feel a little anxious but that is ok. You know that it's your negative thoughts trying to scare you making you feel anxiety. Your brain acts on those thoughts feeding your body adrenaline and making your heart pound for no phyiscal reason.
Remember it is 90% thoughts and only 10% environment that determine the way you feel..
Once I understood that being in control is not being in control all the time I was on the road to recovery !!