I have a method to bury short tails. Not sure if I came up with it or someone taught me. I use it all the time and it has saved me over and over!
Thread a longish piece of thread on your needle...and then thread it BACK thru the same eye, leaving a loop on one side and both tails on the other. Tug on your short thread so you can see the little hole where the tail comes out of the fabric. Put your needle in that hole. As you pull the needle thru, make sure the tail gets caught in the loop. Pull both out , the loop will come all the way out and the tail will be left in the fabric. Trim any excess from the tail. If you have a knot, try a soft tug to see if the knot will bury itself in the fabric.
I hope this makes sense and helps!