Willie Winfield Scott was convicted of possession of a firearm while possessing cocaine, possession of cocaine and obstruction of a police officer. On appeal he contends that the charges of possessing cocaine and possessing a firearm while possessing cocaine should be dismissed because the police officer violated his constitutional rights when the officer seized and frisked him on the basis of a general description provided by an anonymous phone caller. Scott further contends that because the officers seizure of him was unreasonable, his conviction of obstructing the officer should also be reversed. We affirm the trial courts decision because the police officer had a reasonable suspicion based on articulable facts that Scott was, or had been, engaged in criminal activity. We need not address the issue of obstruction because Scott failed to raise the issue at trial as it is now presented on appeal. See Rule 5A:18. Even if we were to address the issue as presented, because we hold the officer had probable cause to conduct the pat down search of Scott we would not reverse the conviction of obstruction.