In order to use the trap, it needs to be set first. Then you leave the trap open for some time, before you check it. When you check the trap, it's consumed, and can't be used again, but you'll get the loot.
#!trap set bear trap
If you're using the Dynobot, it could be wise to set a reminder somewhere in the future, like with:
?remindme Do #!check trap in 4 hours or how long you want to wait. Longer waits equals more loot.