How do I know they replaced my timing belt?

My 2001 turbo subaru forseter, apparently had it's timing belt replaced today. The mechanic said he decided not to install the $600 "kit" that is usually required, as my forseter, with 153 000 kms on it, has all it's seals in good condition. So he apparently replaced the timing belt without using the kit, along with the power steering belt that was looking bad, all for $530. I'm not familiar with the boxer engines for the most part and have done little work on this car over the last 5 years. What is a sure fire way of knowing he has done what he said he has done. Where to look?... Thanks guys.