Perma-Banned for nothing

So this morning i logged onto my account to play a game with some friends, but was greeted with a message that my account had been Perma-Banned for using a "third party program". I don't even know what a third party program means, i'm not very tech savvy and just play league with my friends. My husband even had to build my computer for me; i barely know how Steam works let alone how to hack into League and cheat. I was hoping that this will reach a Riot employee, or someone who knows what i should do. Last week, i had my husband download some mods for Stardew Valley and now i'm worried that those caused me to get banned. I've been playing since season 5 and have NEVER cheated and wouldn't even know how to begin if i wanted to. I don't even win that often, and i was so proud because i made it to a higher rank then last year; could this have caused me to be banned? I was hoping someone here could help me understand what happened, and hopefully how to prove that i haven't cheated.
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