If you are the unfortunate position of losing your passport while you are visiting Puerto Pollensa, you will need to obtain an emergency passport from the British Consulate in Palma in order to gain access back into the UK.
At the time of writing the requirements for an emergency passport are –
2 passport sized photographs
Original airline ticket (printout of your electronic ticket)
The current cost is 79 euros and applications made outwith consulate opening hours will cost 173 euros per hour. (You will be able to reclaim this cost from your travel insurance).