I think all the answers here are excellent advice. I am probably going to use them all. An ounce of prevention is worth...I am about to list a car which will be pick up only so all this advice in going in my ad.
I do think 2 days, I guess now 5 is still a little early to get worried. People are busy these days, many working 70-80 hours a week just to make ends meet, many working 2-3 jobs plus ebay! They use ebay because it saves them time shopping. I had one customer who was in the hospital, car wreck. Things happen. That's why I like all the advice so much. But that doesn't help you now. Just stay in touch, DON"T let it go 4 months!, and believe it will work out. It usually does. We only talk about the ones that don't.
Good luck and let us know what happens!