I thought the same thing. It was in a fairly obvious place to birds so I covered it with a sheath from a sprouting bamboo that was in the surrounding leaf litter.

I was chagrined to find out what it was. I had not seen one before. We had an adult wander through the garden a couple of years ago, so we planted a passion flower. (Should have planted an edible one, but they grow so aggressively it will be an easy mistake to correct.) Last year had a number of adults that looked like they might be ovipositing. So far this year have seen only one adult. That is another story and may have to do with a totally dry late winter and spring.

Anyway, checked it out last night as soon as found out what it was. It was hanging from hind legs, thin, dark and emaciated looking. Barely responded to touch. When I clipped the rose to put it in intensive care he fell off. Put it in jar with bit of wet paper towel and propped him up in fresh growing tip of the passion flower. (At the rate it is growing, the passion flower should reach Oregon sometime next year, btw.)

This morning he looks about the same. I see no signs of pupation. Also, outside in the yard,no signs of browsing on the passionflower leaves, although it may be obscured by the new growth. I will update if there is any good news on the caterpillar. Prognosis looks pretty glum.

It probably came from a nearby passionflower vine that was trimmed a few days back.