I wouldn't worry about it but if it makes you feel better you can use tape or put the screw back in. A little water won't hurt your defender, it didn't hurt the Camel Trophy trucks forging in the river. There are not a lot of water sensitive electronics in the wings.
1983 110 Rebuild
"It is the soldier, who salutes the flag, who serves beneath the flag, and whose coffin is draped by the flag that allows the protester to burn the flag"