First, we earnestly implore Allah to bless the souls of all our brothers and sisters who died in the South Asian quake. We would like also to take this opportunity to remind their relatives to exercise remarkable patience: (And surely We shall try you with something of fear and hunger, and loss of wealth and lives and crops; but give glad tidings to the steadfast who say, when a misfortune striketh them: Lo! we are Allah’s and Lo! unto Him we are returning. Such are they on whom are blessings from their Lord, and mercy. Such are the rightly guided.) (Al-Baqarah 2: 155-157)

Dr. Rif`at Fawzi, former professor of Shari`ah at Cairo Univ., states: In such times of disasters, you are allowed to use the stuff found unless a person claims that these items belong to him. If there is no one to claim such items, then you can use them for yourself, your family, or others.
Here, we have to differentiate between two matters. First, the areas that were totally destroyed and it is not known to whom the stuff belongs. Second, remote areas that were partially stricken or destroyed.
As for the first locations, people can use the stuff that is found without waiting for their real owners who are unknown. As for the second locations, if you can reach their real owners, then you have to keep the stuff that is found until you reach them. You have to advertise those items for a period of time. In other words, the ruling applied here is the ruling of general lost and found items. If after advertising the lost item you did not find its owner, you can use it.
As for the second point you have raised, it is permissible to use items recovered in helping survivors until the real owners of those items appear.

Moreover, the eminent Muslim scholar and renowned Da`iyah, Sheikh `Abdel Khaliq Hasan Ash-Shareef, states: If there is stuff whose real owners are known or can be reached then you should not use them. But if there is stuff whose owners are not known, then you are only allowed to take what is necessary for you because there are other people who may be in dire need of them.

Having said this, relief authorities in such areas are recommended to count the stuff that is found whose owners are not known and to distribute it to survivors – each person according to his/her need.
As for the second point, it is permissible to use such stuff if their real owners are unknown.