Using Up Blank Records In Invoicing Database

I have written an invoicing module for my program and some users in the office are dirtying a record and then leaving the module without completing the invoice. (This leaves behind an almost blank record with a period in one field or a space, etc). When someone else starts an invoice from another workstation it skips this almost blank invoice and starts a new one, skipping the almost blank one. Is there a way to check for these orphans automatically before using another invoice number. This happens once or twice a day so it is of concern to my bookkeeper who checks the sequence of invoices to make sure none are missing before posting them to the accounting program.