A music fan was questioned by Special Branch after sending a text message of song lyrics to the wrong person.
Mr Devine was told intelligence agencies were on "a higher state of alert"
Mike Devine, 35, from Bristol, said he was approached by the officer at work and shown a copy of a message including the words "gun" and "jet airliner".
The bassist in a Clash tribute group meant to text the lyric from the band's song Tommy Gun to singer Reg Shaw - but sent the message to the wrong number.
Mr Devine was not arrested or cautioned, a police spokeswoman said.
Avon and Somerset Police said a Special Branch officer visited Mr Devine after the person who received the message contacted police.
Mr Devine, an engineer at Orange, said he was worried when the officer confronted him a month after he had sent the text.
"I had no idea why they could want to talk to me and so initially I thought it was just some sort of misunderstanding.
"However as we spent about 10 minutes looking for an available meeting room I began to worry about past events in my life. Had I done something wrong when I
was small? Were my parents spies? I was getting worried."
Mr Devine said he was asked if he knew about Special Branch and was interrogated about his mobile phone account.
The father-of-two said the officer then produced a print-out of the text message, which he read out.
'State of alert'
"It read: "How about this for Tommy Gun? Ok - So let's agree about the price and make it one jet airliner for ten prisoners."
Mr Devine said the detective looked "puzzled" when he was told they were lyrics from the 1970s song Tommy Gun.
"We were having trouble working them out but I found them on the internet. I was just texting Reg our singer to see if he thought that they sounded right."
The bass player said he was told by the officer that intelligence agencies were "on a higher state of alert" due to the present climate.
His partner Becky May, 37, said: "He was a little shaken-up and shocked at first. But I think it is quite reassuring intelligence agencies are on top of these things."
A spokesman from GCHQ in Cheltenham refused to comment.