Regrettably Virgin Media do not keep backups for such recovery purposes and if the missing email cannot be located using an email client with IMAP access to the account, i.e. like webmail, then it is unrecoverable.
Edit: when you say in-depth, what did that involve? For instance an in-depth search using webmail would require visiting each folder because its search function does not traverse folders, for example if the email was located under Mailbox > Archive > 2021 :then searching Mailbox > Archive would not find the email but searching Mailbox > Archive > 2021 would.
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