Can I just glue the "fin" thing back onto my dryer?
Find the maintenance manual for your drier. (It may be online from the manufacturer, or there are services which will sell you a download for a few dollars). Unplug the drier, and follow the manufacturer's instructions for opening it up. You'll probably find yourself looking at the drum, with plenty of space to drive screws back in. (You may or may not find the lost screws in the bottom of the machine).

If you don't have sufficient space, follow the instructions for dismounting the drum. Re-affix the fin, then follow the instructions for reinstalling the drum.

Follow the instructions for closing the patient. Plug it back in and make sure it still runs. If not, take it apart again and figure out what you did wrong.