TeraCopy error message: "Operation did not complete ... file contains a virus", yet my antivirus did not prompt me about any detected viruses

TeraCopy in all probability only reported an error message provided by windows as it's a standard windows error message.

0x000000E1 ERROR_VIRUS_INFECTED Operation did not complete successfully because the file contains a virus.

And windows probably got it's information from avast.

You shoud try to scan the file manually with avast and delete it if it contains a virus.

Windows error codes