Okay, my next suggestion. Leave a note of your own, folded and jammed between the seat and tank. Make it polite, but condescending. Apologize for parking so close, as you know he must have paid a whole lot more for his bike than you did for yours, and he must be very protective of it. Make some comment about the cost of upkeep, as it is obvious that he doesn't work on it himself. Then in a separate paragraph, get mean. Tell him in no uncertain terms, that if he EVER tapes anything to your paint again, you will rip his lips off, or staple his nuts to a fence post. Something so outrageously funny to us here in the forum, that he may take it as funny, but will still get the point.
I now open the floor for ideas for that threat