why do i play as champions i don't own or isn't on free rotation in aram

Okay so whenever I play ARAM, I sometimes get champions I do not own at all or that isn't on the free rotation for the week. Like i'm pretty sure it's a glitch because the primary skin of the champs, there's a lock icon shown on the primary skin of the champions. This has been going on for 2 months now. And it's really annoying, I have no idea why it's like that.

For the 23rd of Monday to Monday 30th 2018, I get Tryndamere, Ornn and Leona who I don't own at all and aren't in this weeks free rotation week.