If you lose your passport, or other documents, you will need to report this to the Police and UK Visas and Immigration as soon as possible, and apply for new versions.
Always keep your passport and visa in a safe place and, if travelling, take extra care when in crowded areas.
Never keep your passport or BRP card in an outside pocket or backpack. You should also keep a copy of the main identity page of your passport and your student visa somewhere safe in your accommodation.