RCQ: opponent had Welding Jar placed next to lands, I forgot about it and misattacked. What do the rules say about permanent placement on the battlefield?" | tcgmode

Hi, on my last RCQ the following happened to me. My opponent was playing Affinity, he was playing quite nicely, but he was placing all artifacts next to the lands at the bottom of his playmat. Important: he played a Welding Jar on turn 1. Honestly, at first glance this didn't seem like problemati...