This has occurred to people! But if you run the numbers, they are still not good enough in that early (~100 My) window when stars in the parent nebula are close together, you get something like 1 chance in 1000 of possible panspermia events (based on modeling lumps of rock flying back and forth). Not terrible odds, but nothing like the Mars -> Earth odds.

A more extreme version of this is the idea of panspermia in the early universe, when the cosmic microwave background radiation was warm enough to keep water liquid: https://lweb.cfa.harvard.edu/~loeb/habitable.pdf

I knew I couldn't be the first, but I was more commenting on the lack of discussion I've found in the peer-reviewed literature!

The key was to change "nebula" (returning results for "stellar nebula") to "star forming region."

https://journals.sagepub.com/doi/abs/10.1089/ast.2005.5.497