I overpaid my student loan payment by $2000 (typo), do you think I can get it back?

Sure. Talk to your bank and to Sallie Mae. You can work it out, but it will probably take a couple of weeks. Speak to them Tues first thing, be prepared to HOLD. If you get nowhere, ask for a supervisor. Be pleasant, businesslike and apologetic......it was YOUR mistake not theirs.