He might not have been the one to find the property, but he surely was responsible for helping you construct the offer, negotiate terms and assist you in a smooth close of escrow. Knowing Buyer Agents there are many more things he helped with that you might not have noticed. If a problem came up during the purchase, it would be his legal team that would be called upon as well.
I'm sure he worked very hard, as most Buyer Agents do,. In my opinion a person should be paid for their work, don't you agree?