2023 sienna platinum ECM burned out

Hi all, so I have owned this van for about 17 months and battery has given me problems since a few months into me owning it. It goes dead all the time like if the door gets left open...lately, it's been cold here and it wouldn't start just presumably b/c of the cold. Anyhow, this time I couldn't get it going at all. I've been using a jumper pack occasionally, which as a professional landscaper, and mechanic, I know how to use the thing. Now the ecm is burned out and toyota says I must've hooked it up backwards. This is not the case! Anyone else heard of an ecm getting cooked and supposedly giving codes that it was hooked up backwards? Please help, I can't afford this and I'm certain it didn't happen the way they think it did.

Thanks all