tourists were rushed off liverty island by boat operators just after midday friday after a 911 caller said he was ` going to blow up ' the landmark .
police sniffer dogs then seized on a locker on the island , which they thought contained something suspicious .
the nypd 's bomb squad was scrambled , but a full search of the island finally failed to find .
the park 's 4 pm closing time had passed , so visitors were not allowed back .