To be fair they hired security so I don't think they'll let the house burn, bet now they pay them fat cash just to keep footmarks off the grass.
However, fuck everyone involved with the seizure of the rifle, steppers get stepped on.
I've thrown away plenty of lowers by accident and forgotten about it so it's definitely a possibility. I've never heard of a bull taking parts though, only full guns. I'd check the cameras in and outside the house, she might have hidden it just to piss you off.
Always check the washer and dryer, I've lost so many socks and lowers in them.
That being said, hopefully you find it a stupid spot that you didn't even think of, I'm sure as soon as you get another one to mess with you'll find it.
Go on offer up and craigslist for your local area, got lucky because I'm in phoenix but I found two local guys that were selling plates on there. One took a bit to respond but the other sold me level 3 plates two days after I hit him up. I got a plate carrier and a trauma kit, fuck larping they're rioting in neighborhoods. It might not be the best plates you can find but at least you'll have one if a bullet heads for your chest.