What is the law pertaining to bags or something else been exchanged by mistake?

If someone’s shoes got exchanged in a masjid or someone’s bag got exchanged in the airport and by mistake he got someone else’s bag by him, then it is not permissible to use that bag or shoes. Because there is no clear proof to say that this bag or shoes belongs to the same person who took his bag or shoe. And even if the case is such, still it is regarded as a luqata because there was no mutual exchange in the transaction. It will be necessary to look for the owner. And if he can’t find the owner then he should give it in sadaqah on behalf of the owner, and if he’s poor himself then he may take it. Note: Luqata means a lost item found some where.