Hi,
We're working on fixing the issues surrounding making sure unsaved files are preserved even in the event an R session crash. In the meantime, there is an R package which might be able to recover these files for you: https://github.com/jmcphers/rsrecovr
tl;dr:
remotes::install_github("jmcphers/rsrecovr")
rsrecovr::recovr()
to restore all the files in your project.
Please let me know if this works for you. And I apologize for the inconvenience.
-Andy