If I brought a miniature back pack will it get searched?

No

I haven't experienced a bag search and I have a large purse

Just put your jacket over it and it shouldnt get surched under the jacket

If the bag doesn't go below your elbows, you should be good to go

Well, I've never seen them search purses, including small purse-type backpacks. I've also never anyone come in with a regular backpack. I think you'd be fine.

My purse looks like a backpack and I never get searched