In the campaign when we receive an out of office response-

If the response comes within a few minutes, the recipient will be in the campaign and will receive the next touchpoint. In the case of out-of-office emails, this is usually the case, hence the recipient will receive the touchpoint.

If the response comes after a few minutes, the candidate will be removed from the campaign. This happens rarely in the case of out-of-office emails though.

To add them back, go to the candidate profile, delete the campaign from the profile and add them to the campaign from there.

However, they will be added to the campaign from the start.