Here's a link to a website with a .PDF copy of the manual (another hat tip to Steve; thanks again for this valuable resource!).
First column, 4th item down from the top. Click to download, then save it to your computer. There's not a lot of info on disassembly, but if you're mechanically inclined and/or know someone who is a bit of a firearms enthusiast, you should be able to figure it out.
EDIT: Now that I've read it more closely, however, it looks like disassembly (page 8) only covers removal of the slide; I'm thinking the pin you punched out was in the frame, right? (The part that fell out appears to be the ejector, and I believe it is frame-mounted).
Remove the slide using the procedure in the manual, so you can see and access the slot in the frame where the ejector is usually mounted; tap the same pin part-way out, then hold the ejector in place (hook-shaped-end on top, pointing toward end of barrel) while someone else taps the pin back in. Assuming that pin doesn't hold anything else in place which moved when you took it out, you might be good-to-go.