I received a delinquent bill from the Philadelphia dept of revenue and need access to receipts proving that I paid my 2012 and 2013 state income tax.

Your only proof would be your bank statements or credit card showing the payments coming out.  Turbo Tax has no confirmations of paying any tax due state or federal.  They only send your bank account info with your return for the state or IRS to pull it out of your account.  But most states don't let you pay by Direct Debit only by check or directly on the state website.  Only you can provide proof.