Will apple still replace my iphone 4 if it has been opened?

I got my iphone last august and it worked fine until my lock button broke. My phone was covered under warranty so apple replaced it. Lo and behold, my lock button broke once again this past week. I went to a verizon store to see if they could replace it again since I thought it was still under warranty. Turns out they told me my phone was no longer under warranty. I asked if they could check again because I got my phone last august and they said they were sure it was out of warranty and there was nothing they could do. The nearest apple store is about 45 minutes away from my house, and since I thought the information verizon gave me was correct I didn't drive all the way to the apple store to hear the same answer. So I went to a third party repair shop. The guy opened my phone up and looked at my lock button and said the procedure would be complicated to fix and that it would be very expensive so I decided not to have anything done and he put my phone back together. I got home and got onto the apple support website to see where I could go from here since I don't want a broken phone for another year. I chatted with a representative in the chat room thing. I gave him my phone's serial and MEID number and he said my phone was still under warranty! I was shocked because the person at Verizon told me I wasn't under warranty and there was nothing that could be done. The apple guy told me that I could get my phone replaced and all I had to do was go to the apple store and swap it out for a new one. My question is, will by warranty be voided since I went to a third party repair shop? My phone wasn't fixed the guy just looked at it to see what the problem was and then put it back together. I know that once you do that your warranty is voided, but I feel like I am in a special circumstance since I did it thinking I was out of warranty since that's what I was told at Verizon. What should I do?