Audit by Phone
I think you could do a documentation audit via FAX and e-mail, depending on how the records are kept. If the records are electronic, have them send copies via e-mail. If the records are hand-written, send them via FAX. You would have to rely on the person at their end to send you an unbiased sample of records.
You could certainly question them about the process over the phone, but you would be at a disadvantage since you could not see the process "in action".
Regardless, I think you would have to document that the audit was not in person. I would not always do the audit this way; you could do it this way this time, and go on-site for the next time.
Just as a safeguard, you may want to ask your registrar for their opinion.
--Jodi