Guava cache returns empty result on second hit

I have strange (at least for me) behavior with guava cache. After the first click, the following calls return an empty object. I have not used the strange extinction, so I can not understand where I am doing wrong. I declared the following LoadingCache:

LoadingCache<String, Vector<Location>> locations = CacheBuilder.newBuilder()
            .maximumSize(100000)
            .build(
                    new CacheLoader<String,Vector<Location>>() {
                        @Override
                        public Vector<Location> load(String key)  {
                            return _getLocationListByTranscriptId(key);
                        }
                    });

and I used it only in this method:

public Vector<Location> getLocationListByTranscriptId (String transcriptid) {
    if (transcriptid.equals("TCONS_00000046"))  System.out.println("tcons found, will this work?");
    Vector<Location> result;
    try {
        result = locations.get(transcriptid);
    } catch (ExecutionException e) {
        System.err.println("Error accessing cache, doing the hard way");
        result = _getLocationListByTranscriptId(transcriptid);
    }
    if (transcriptid.equals("TCONS_00000046")){
        if (result.size()==0){
            System.out.println("this is a problem");
            return null;
        }
        System.out.println("this is good!");
    }
    return result;
}

Iterating over the collection of input string, I get the following output:

tcons found, will this work?
this is good!
tcons found, will this work?
this is a problem

So, the first time I use the cache, it works, but A) the value is not correctly stored for future calls; B) the value is reset for some strange behavior. What can I do? Thanks everyone for that!

EDIT: axtavt , . , , , guava . . (, ).