Ideas.... well OK.
If your boat has mast that can be lowered, i.e. via a pivoting base, it could be laid down on deck. There are probably sister ship owners here that could guide you on that. If it does not have a tabernacle or other means to pivot, then you need to lift it straight up a half foot and then lower it down on deck.
Imaginative sailboat owners, with planning, helpers, and strong nerves have commandeered high bridges to jury rig such schemes... I know of a boat owner that even did the trick of having two helpful larger neighbor boats, rafted up against each side, using their spin halyards to gently and slowly hoist his mast straight up off the step. (I would have to be quite desperate to try that one...)
Hopefully some other sister ship owners can chime in with more useful notions.
Good luck,
Loren