If you're considering buying a flat where the seller has lost the possession and allotment letters, it's crucial to proceed with caution. The seller has filed an FIR for the missing documents and suggests a newspaper advertisement. While a title search and publication in a newspaper can help, the most important document is the Conveyance Deed. If the seller possesses this, proceed carefully after advertising for objections. However, if the Conveyance Deed is also missing, it is strongly advised not to purchase the property.