Hello Vasilena,
I personally ask my guests to send their national ID or passport after a reservation is confirmed in order to include them in the house insurance before their arrival.
A friend of mine who also hosts with AIRBNB, asks for a copy of his guest´s IDs because there is a 24h security in the building and the guards are notified of the guest arrivals days before it occurs.
So I guest that the only way to be safe in this case is by reading out the overall reviews/opinions of other guests that have stayed in the same house.
I hope your stay in Madrid was a pleasant one!