I got DC-ed for about 5 minutes and didn't get EXP when the match ended

It's a simple, yet weir thing. I played almost 40 minutes game where I've DC-ed about 20 mins into the game because of a power outage. I came back ASAP and played normally till the end. Yet, when the game ended I saw that I didn't get any EXP and a notification that I can't receive rewards due to AFK behaviours. Should it be this way? Or is it a bug? Here's a screenshot: https://imgur.com/a/iLDJOZ2 And yes, I do know I'm a garbage Lux player.
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