The command "git checkout -qf <sha1>" failed and exited with 128: "reference is not a tree"

Reach me here:
@jeroen and @jimhester --Not sure what the error means, given this thread at end of build that errored out/aborted:

error: fatal: reference is not a tree: 7308c9f58b5e0cd0256f125ec03ba871cb29f60c

----------------- start of trace ------------------------

146Installing R


7760.87s$ git clone --depth=50 --branch=main suszanna/heu3

777Cloning into ‘suszanna/heu3’…

778remote: Enumerating objects: 44, done.

779remote: Counting objects: 100% (44/44), done.

780remote: Compressing objects: 100% (39/39), done.

781remote: Total 44 (delta 12), reused 0 (delta 0), pack-reused 0

782Receiving objects: 100% (44/44), 612.32 KiB | 4.67 MiB/s, done.

783Resolving deltas: 100% (12/12), done.

784$ cd suszanna/heu3

785$ git checkout -qf 7308c9f58b5e0cd0256f125ec03ba871cb29f60c

786fatal: reference is not a tree: 7308c9f58b5e0cd0256f125ec03ba871cb29f60c

787The command “git checkout -qf 7308c9f58b5e0cd0256f125ec03ba871cb29f60c” failed and exited with 128 during .


789Your build has been stopped.

This means that the commit does not exist – most probably, has been deleted since with a forced push.