Well, I did it: left my rod leaning against the car and drove off. This was at Patuxent River State Park on Saturday afternoon. If I didn't run it over, there should be (or have been) an Orvis Clearwater 8.5' 4 wt. I know it's beyond a long shot that someone reading this could have found it, but if so I'd be grateful to hear from you.
If I don't hear from anyone, I'll probably take a drive up there this afternoon, but with very little optimism.
Fishing report as long as I'm here: it was a lot lower than a couple of weeks ago, but I still managed several brown trout from tiny to 11", lost a couple of nice rainbows, and (as usual) caught my quota of fallfish. Nearly all of that was on a hare's ear variant. I saw very few rises, and I think what I did see rising were mostly fallfish.