Is recipient liable here ?

ya ofcourse the service recipient will be liable to pay servc tax under reverse charge

The company should have discharged its share of the ST liablity.

To correct the error that is already done, the best thing for the company to do is take a letter from the Security agency stating the details of ST Lability discharged by the security agency and produce if there is audit or if it is called upon. The dept should not have any objection as the full ST liablity on the particular invoices has been discharged.