You can restore table records in the menu /Administration/Search/Database log, filter on your tableId (345 for Purchtable) then filter on type of modification, delete in your case, search the record you want to restore, go to to the history tab, select it and click on the reinsert button.It will regenerate your purchase order. This works in AX 2009.
Hope it helps, please verify solution if it solves your problem.
Thanks Thomas for the solution . Is it Administration -->Inquiries --> Databaselog? But the table was completely empty. There was no records.