How do I discreetly tamper with a glue trap for mice and rats?

If you just want the glue to be less sticky, vegetable oil should do the trick. That's what is recommended for freeing a trapped rodent from a glue trap. Cat urine or something else with the scent of a predator might also scare the mice away from the trap - my rats refuse to come near me when I've been handling my friend's ferrets. You could also get some live traps and catch the mice yourself, then release somewhere away from your store.