Steve telling Rich: "I'm never going to forget you bushed out on me." "bushed out on me" is a bit negative and very informal. When someone "bushes out on you", it means they're leaving you or taking off at short notice with no apparent reason and leaving you little time to find a replacement and so making things a bit difficult for you. It is a negative statement saying you are heading off, who knows where, with no warning and thus leaving me with a problem. Here Steve is unhappy because Rich is taking off at little notice or warning and leaving Steve the problem of finding someone at very short notice to do the work shifts Rich was to do. Rich saying to Steve: "Get down off it" means "Stop making more of it than it is. Don't exaggerate, it's not such a bit deal as you're saying. Again, this is very informal. If you're interested, I think this expression is derived from the expression "get down from your high horse". If you google that you'll get some answers for that as well.