Many counties, especially the busy ones such as Alleghany and Philadelphia, have issues of not properly expunging the record. It does take a little while for it to be cleared as the state police are often backlogged with expungement orders. The least accurate, but quickest way to check, is by going onto www.ujsportal.com. This is not always accurate, but if you are anxious to see if it is on there this will give you some insight. You should also try to get a copy of your records from the state police, to confirm that the online record is accurate. This could take a while. You can contact the attorney that represented you on that case and they may be able to provide you with more information if you can contact him/her.
Look in the public records or the clerk's website. If you can find it they haven't done it yet. Usually that is a separate proceeding. Meet with your lawyer and confirm it s automatic.
The fastest way to get your answer is to contact the attorney who represented you. S/he should be able to find out relatively quickly whether your record has been expunged.
As a previous poster suggested, the UJS portal is the next best option.
If you REALLY want to be sure, you can request a copy of your criminal history from the PA state police. Google "criminal history PSP" and you should find the correct website relatively quickly.