Is it bad to look at a friends texts to see if i was being made fun of?

Yesterday i had a friend over and he was talking to one of our good friends. We wanted to go to dairy queen and so i told him to text our friend to come. She couldnt because she was at the country stampede. So we decided to go anyways. When we got back he was still talking to our friend. He wouldnt tell me what they were talking about, and i didnt know why. So i woke up this morning and hewas still asleep. So i looked at his phone to see what they were talking about. When he asked if she wanted to go to DQ with us he said " i dont blame you if you dont want to" and so i read on, his next message said " hes awkward so uou dont have to". Im very disapointed in my friend cus we have been very good friends for a long time. So i saw my name mentioned in another message to a different friend. The conversation between the two was, my friend at my house begging ti hang out with the one he was txtng because he didnt want to go with his other plan (which was going to my house), but then my friend woke up so i had to make up a lie about why i had his phone. Was i in the wrong to check his phone?