Personally I have no idea. I expect if your work visa has expired but you are studying over here, the immigration people aren't that bothered with you providing you aren't working. If Scott hadn't gone abroad and had to pass back through official channels, or I guess came back into the country as a tourist, the issue probably wouldn't have arisen. Like I said, I'm certainly no expert on matters, I'm sure there is someone on here who knows more about such things than me but I'm guessing it's just unfortunate, possibly compounded by a little naivety.