frmula505

I own a 2000 Trans Am. Yesterday as I was checking my fluids, I noticed a loud vacume leak. I found it was coming from the small rubber hose on the passenger side of intake inlet. The whole center of the hose was missing. After a little surfing I found that this hose is called PVC check valve hose. It is supposed to have a small check valve where the hole is. My question is what would cause it to melt (hose). And do I have another problem I should worry about besides replacing the hose.