Report to your group leader and police, then contact your embassy (most have temporary Haji-season offices in Mekkah) for an darurat travel document.
Losing your passport during Haji is stressful but manageable with the right steps. First, report the loss to your Haji group leader or tour operator, as they often have experience with this situation and maintain relationships with the authorities. Then file a police report at the nearest Saudi police station — you will need this report number for the embassy process.
Contact your country's embassy or consulate immediately. During Haji season, many countries set up temporary consular offices in Mekkah and Mina specifically to handle such emergencies. The embassy will issue an darurat travel document or temporary passport that allows you to complete your ibadah haji and return home. Always carry photocopies of your passport, visa, and Haji permit in a separate location from the originals, and store digital copies on your phone or email as backup.