Loosing your bitcoins due to a glitch on your mycelium app, and how do you get the back without a backup?
If you do not have a backup of the wallet, either in the form of seed words or a exported file from Mycelium, then your coins are permanently lost.

Ideally, one should be backing up and restoring their wallet to make sure they've got all the necessary information before sending a significant amount of coins to it.