Ok! Don’t worry! The deleted videos off from this camcorder are not actually erased as you think. They are still there, on this camcorder and only become inaccessible and invisible. So, you do have chances to get them back before you rewrite them with any new file.
You should try to recover these deleted videos back from this camcorder with a camcorder data recovery freeware:
Remember to be careful about your important files next time.