One thing I don't get in the new Star Trek movie?

Okay, so I've watched the DVD like 20 times now. Obsessive, I know. But there is one part of the movie that I just can't understand. When Kirk's escape pod lands on Delta Vega and he finds Spock hanging out in the ice cave, they have a little chat and Spock tells Kirk that he needs to get back to the Enterprise. So they walk to the Federation outpost, and Scotty and a little green alien guy appear to be the only people at this particular facility. They never explain exactly what the purpose of the outpost is, just the fact that Scotty suspects he was igned there as punishment, basically implying that there were some sort of questionable 'official orders' placing him there and requiring him to stay there. So why is it that after Spock (basically) sets up the transport, Scotty beams WITH Kirk to the Enterprise? I mean.. other than the obvious answers such as 'he didn't like it there on the icy planet' or 'he was really hungry'. Wouldn't he basically be abandoning his post? Wouldn't he then get in trouble for that by Starfleet? Its not like they wouldn't find out. It just seems strange and out-of-place to me that he would make such a bold and deliberate decision to invite himself along to the Enterprise without even asking anybody or anything. Maybe its just me..