Weird Sponge on the Back of the Distributor

I just finished replacing the o-ring on the distributor shaft. When I cleaned the back of the dist(the flat side that touches the engine head), I noticed a small piece of sponge(?) glued (maybe because of the heat) next to one of its corners, but most of it was placed between the distributor and the head. First I thought it was some marking that was left by a mechanic, so I removed it. Now, I am a bit worried that I might had removed something that suppose to prevent oil from leaking out. Although it seems that it doesn't belong there, I don't think that anyone removed the distributor before, therefore it might have been there originally. Please let me know if you noticed anything similar when you took out the distributor on a 3SFE engine. Thanks.