HTC One M7 :: Contacts Disappeared On Phone

I got an HTC One two days ago and transferred my contacts, music and photos from my old phone (a Samsung Galaxy S) using the HTC Transfer tool. It worked like a charm - or so I thought. After trying to send a text today, my entire contact list was completely gone, and the phone is telling me it has zero contacts stored in either phone storage or on the SIM card.

The contacts were there four hours ago. My call history is also deleted, but my texts messages are still saved. Even stranger is that the photos and music that were transferred are still there. Luckily I still have my old phone and can transfer the contacts over again, but it's odd this would happen at all. I'm wondering if it may have to do with google+, as I switched over sms to google+ hangouts this morning on the phone (but I can't see how this would make a difference).