Here are some pictures of the ESC. I don't think it can be salvaged. The middle row of FETs looks burnt beyond repair. The white stuff on top of them is thermal paste that came off from the heatsink.
Heatsink;
Yep, that's fried. That has happened to me with a few ESC and the cause was bad timing set on them. The latest one was a 60A ESC from Hobbywing and I was using it with a 6 pole Mega. I made a mistake of changing the timing instead of another setting so one phase burned out. With the 4 pole Neu Y motors the timing should be at middle. Please send the unit back Lito.