Sanity check 1: Are you using version control? If so, you may just want to revert to an earlier commit.
Sanity check 2: Do you make periodic backups? If so, you may just want to revert to an earlier backup.
If sanity has failed us today, then here’s what you do:
- Go to your
Content
folder of your project and find theYourBlueprintName.uasset
file and delete it. - Open your project, which should complain about a missing blueprint, but not crash.