Pumpkin, at that size and stage, I don't think can be saved.
Plant another seed(seeds) it is easy to germinated them.

Second, I would direct sow them where they are supposed to be growing.

Are you in the southern hemisphere ?

Ah crap. I bought that one as a pack of 4 seedlings from the supermarket and it was the only one that had survived (the rest i'm pretty sure were eaten by snails). It was already in the ground. Luckily I've been drying out some seeds that are just about ready.
Yeah, I'm in Australia. So it's just entered spring.

Keep it watered and see what it does! I've had pumpkins eaten almost to the ground by snails or slugs come back. It might happen! Nancy