My friends and I had this problem about a year ago and tied a rock to a rope to make a poor man's throw line, threw it over the plane, and pulled/wiggled it until it got dislodged. This happened twice to two different planes and this strategy worked both times, although in both cases the planes weren't stuck super deep in the tree.
I've been thinking about getting a legit throw line for stuff like this though, because the rocks we chose kept coming loose