You have up to 14 days to complete the MDS from ARD. So, the best way to approach this is have another person (preferrably from the same discipline) reassess, do the CAAs, and enter their own signature. If the result of the resident interview/s is unknown, skip that section and just do the staff assessment.
If crunched for time, leave Z0400 unsigned. Document reason, review the assm't w/ another person (from the same discipline or the the entire IDCP) for correctness and the CAA for relevance then both sign the document. Often, more than one discipline completed a care plan yet V0200C only allows for a single signature. The RN coord. can sign it, too.