I'm having trouble with a rat too, my friends mother in law got one in her kitchen, had it for over a week now, and they havent used it since.
They called me after a week as rentokill couldnt get him.
I ferreted the kitchen to see if they could track him down, no luck. So set spring trap and live cage trap.
I returned, spring trap had been triggered and blood all over it, but no rat, followed the trail of blood, under the scurtain of the kitchen it went. Ripped the boards up and had a good luck, put ferret under to investigate, but nothing.
Turned the whole kitchen upside down