While it's inconvenient, there's no reason you can't resolve this yourself.
The transmission fluid pan has a single-use gasket on it, if you just bolt it back on you run the risk of fluid leaks, which could lead to a very expensive problem if you run out of fluid.
While you could bolt it back on and chance it, the better thing to do is to take it off all the way, and do the routine maintenance tasks of a transmission fluid change, which is totally doable at home:
- Replace the transmission fluid filter
- Check for metal in the pan and clean any shavings off of the magnet
- Clean the pan edge and transmission housing edge thoroughly to get all traces of the old seal off
- Pan the back on with a fresh gasket
- Refill with fluid
The filter and gasket should come as a kit, some kits will also have the right kind and amount of transmission fluid as well. A fresh filter and fluid will extend the life of your transmission, so it's good maintenance anyway. There are videos on the web for your make and model, have a look and see if there are any gotchas, it's usually a straightforward process though.