Premium Chest???

So. A few months ago, I created a new account (actually it's the account on which I'm log on to write this), had Evelynn (my favorite champion) and Twitch, and then, the hextech patch came (or whatever, I don't remember the timeline), and so I opened the free premium chest and got masquerade Evelynn, a legacy skin. I was so happy, got her to mastery 7, but I eventually got banned due to my behavior. I thought back then that the skins we got from chests (even premium) were pure random, and that I had just got super lucky.

So I decided to create a new account, bought singed because I felt like it, and got a singed skin from the premium chest. Then I knew it couldn't really be random, and did my research and found that it is common knowledge that the premium chest gives you a skin of a champion you own.

So then I decided to create another account so that I could buy Evelynn so that I could have a skin of her again..... I happened to unlock the chest feature right before I bought Evelynn, then I opened the chest and boom, a damn Varus skin (which I didn't own)........ It got me mad as Evelynn was the only champ I owned when I opened the chest, but I convinced myself that it must have been because I bought Evelynn after acquiring the premium chest (still before opening it).

So then I decided to create ANOTHER account so that I would buy Evelynn BEFORE reaching lvl 5, so that the chest would give me an Evelynn skin. But my account glitched or whatever (I don't recall reaching lvl 5 but when I log on one day I was lvl 5 with 0 exp), but still bought Evelynn even though I had already acquired the chest, I then opened the chest and BOOM, an Hecarim skin (no, I did not own him).

So then I yet decided to create ANOTHERRR account on which I would definitely buy Evelynn before reaching lvl 5 (did I tell you Evelynn is my favorite champ?). And I succeeded! I played 1 game per day for first wins, and got Evelynn at lvl 4 (that was yesterday). I then reached lvl 5 today, and when I went to open the chest BOOM, there's an error on rito's side that makes me unable to open it. I passed all day trying to open the damn chest and it wasn't opening. Then, when I came back from restaurant a few hours ago, I tried to open the chest.... And it worked!!! And guess what? I got a Mordekaiser skin, wooooo, exactly what I was NOT aiming for.

So all that story for one thing. DOES THE DAMN PREMIUM CHEST REALLY GIVE YOU A SKIN FOR A CHAMP YOU OWN!??!? EVERY source I found on the internet says so. But 3 times in a row it doesn't. The only actual rito staff member that said anything about it talked about that skin being "semi-random" (his words), I dont remember where. What the hell does that mean??? I haven't seen a single person with my problem, everyone I read about said they succeeded into getting a skin of the champion they own.

What the hell is wrong!?!!?!??!!?!?!?!??? Can someone from riot say clearly if THE PREMIUM CHEST REALLY GIVES A SKIN OF A CHAMPION YOU OWN 100% OF THE TIME???

I'm running out of summoner name ideas, and goddamn e-mail addresses. The first account of my story is actually my 6th account btw, and I'm sick and tired of creating new smurfs.

Thank you for reading the story of my life. Yes, is my life, rito give me my damn Eve skins.