Is he lying or not?

So me & my husband deleted our facebooks in 2013 when we got together. We haven't made one or anything. Well last night we got into cuz he was showing me this new theme he had on his phone & when I was looking at it I saw Facebook messanger. Then saw the Facebook app. I asked him about it & of course it became a fight. He said he didn't know how it got on there. He said when he updated his phone it just appeared on there. My opinion is that there is no way it will just automatically appear on there. You have to download it.i even told him that & he said well it just downloaded itself. I was like whatever. & went to bed. So in yalls opinion do y'all think he is lying or should I believe him?