sPFLib/src/main/java/it/polimi/spf/lib/search/SPFSearch.java
public SPFPerson lookup(String identifier) {
		boolean isReachable = mSearchInterface.lookup(identifier);
		if (isReachable) {
			return new SPFPerson(identifier);
		} else {
			return null;
		}
	}
public SPFPerson lookup(String identifier) {
		boolean isReachable = mSearchInterface.lookup(identifier);
		if (isReachable) {
			return new SPFPerson(identifier);
		} else {
			return null;
		}
	}
Allows to retrieve a reference to a remote person given its identifier.
This reference is valid until the given person is reachable from the
proximity middleware.

@param identifier
@return