Just an idea taken from the fact you said you were laying down and assuming you were in bed...
most likely on the verge of sleeping?
If that is the case, you could have easily had an hallucination caused by low
brain waves such as being around the theta state...one way to tell is by how you felt.
Did you feel an uncontrollable fear or anything like that?
Or can you say honestly that you were awake enough to not have any hallucinations?
Hallucinations tend to be fearful things ( for me anyways ) learn to think before feeling...
that way you wont go crazy fearful on something popping in your window so you can think
rationally

edit on 21-6-2011 by MajorTom4754 because: More info<3