Accountant gone AWOL

One of my recent client is having real problems getting hold of his previous accountant to get all his paperwork back. 

The clients total  VAT reclaim on his purchases was disallowed since he did not produce evidence of purchase invoice for a van.

The client has tried contacting the accountant several times. The client knows that the accountant is abroad doing some charity work. He does not know when the accountant will be back. It has now been a two months.

I wrote to HMRC explaning the situation. No response on this.

HMRC are chasing (debt collectors) the client for the full VAT on his sales without deduction for purchases. He explained the situation to them. They just advised him to change accountants.

What can be done

- Get HMRC off the client's back for a month or so?

- If clients is not able to get the documentation from the previous accountant on time.

Thanks