I gotta say I can't believe I'm stepping up for this guy, but I too had some trouble with my wrx dipstick after I changed my oil at 3k. Oil in, no real oil "line" on the stick, in my level garage. Huh? Added more, still nothing. Wipe, insert, repeat. Weird. I drained a few quarts (messy), and tried again. No problem at that point. I'm guessing I overfilled it so much that it was off the stick.
Now, stupid mistake yes, but I fixed it. I've been changing my oil (along with swapping trannies, engines...) for over 13 years, so I have some idea how to change oil.
That said, this is not the service station guy's fault, it's yours. Tough to swallow, but it sounds like you're probably OK. I go along with the catastrophic failure theory, which you avoided. As kturner said, do it yourself, always.