HMRC can, and do, request to see the original copies of any and all receipts that are in a direct relation to a business expenditure of a business/company under review.
The individual inspector can agree, and mostly do, to view the receipts at the accountants office, business address or pretty much anywhere in the UK. But under the legislation, different acts which are dependant upon which head of tax the inspector works under, the HMRC has the right to demand that all information they require to complete their review is provided. If it's not then they will just estimate their figures, which will more then likely work out more costly for the tax payer, and lump on penalties for failure to provide the information and interest.
So his excuse could be valid. But all in all I'd say the lad is a thieving pikie c**t. Hope you get it sorted, and I'd personally go down the small claims court route.
p.s. Sorry for the long post just wanted to clear up the mis-information about the receipts.