Also had similar, caught a domain, was contacted soon after by the previous registrant asking if they could have it back. As it happened, they owned the trademark worldwide, but as it was two generic words that worked together, they knew it wouldn't be that easy to recover through legal paths. They asked how much I would like, I said make me an offer because otherwise it may be seen as domain hijacking. They made an offer which was 'reasonable'; I could have pushed for more, but felt from the long conversations we had it was an honest mistake, so deal done and both parties happy. Just checked, they still own in, but the risk of your generosity could be a ploy where they sell it on for a tidy sum!