No. The store must attach the receipts to the voucher in order to be reimbursed by the airline - and they are reimbursed only the actual amounts for goods sold excluding tax/VAT.

I get to review and sign off on all the invoices from delayed flights at my airline so I am highly familiar with the process. It is also quite amusing to see some of the stuff that people have purchased in lieu of refreshments (my favourite is "edible underwear" from LaSenza claimed to be "Food").