There is a feeble chance of rejection. The signing in the admit card is just to verify that you have attempted the exam and to have a receipt for you. Not signing it doesn't mean you didn't gave the exam because if you don't given the exam how does the marks corresponding to your roll and admit number get recorded. So there is practically no chance of rejection in seat offered.

You will get more confidence if you just compose an official mail discussing you problem with the authority of Puducherry University and they will obviously give you a more accurate explanation.

Don't be tensed!

I hope my answer helps you. All the very best for your future endeavors!