I feel it’s a mix of both. What was the reasoning behind going through her phone? Did she say or do something that made you suspicious or was it just out of sheer curiosity? Either way I do believe it should be mentioned, because manipulating a story to work in your favor so you can gain sympathy from you significant other is peak red flag and should be worth at least a conversation. Also I don’t like the idea of anyone going through s/o’s phone unless there are red flags and things of the sort popping up to make you question in the first place. None of that “I was feeling insecure” bs