Hi, I have a solid which I have a mask on (to cover an element of the video). I then click on the video layer and track motion. So far so Good. I then Edit Target and set the target to the layer with my solid. The solid seems for of vainshed (it actualy vanishes when I first clicked on the video layer, I thnik), what ever I do I cant get it back. Ive tried this several times without any luck;(.
Nobody can say anything concrete without seeing some screenshots. Chances are you simply didn't take care to adjust the anchor point and/ or your layers and comp are of different size, resulting in values that send your solid far beyond the edge of the comp or something like that...
The best thing to do would be to apply the tracking info to a null object and then parent your solid to the null.
That being said, I agree with Mylenium, that you probably just sent your layer outside the comp window accidentally.