Arthur McGarrigle, the NASUWT's honorary secretary for the province, had been speaking about bullying to delegates at the union's Belfast conference just hours before his son, 23, discovered the anti-personnel device.
Mr McGarrigle hurried the 90 miles back to Strabane to find police surrounding his house.
The bomb was thought to be the work of a small group of republican dissidents who object to Mr McGarrigle's position as an independent member of the local district policing partnership.
"I was speaking out against cyber bullying for most of the day," Mr McGarrigle said, "and then became the victim of old-fashioned bullying myself. It was a case of 'We don't like you, so we'll burn your house.' "
He said he had been particularly concerned for his 11-year-old daughter, who could easily have picked up the brown-paper package, thinking it was a birthday gift.
"It is the first time the NASUWT conference has been held in Belfast," Mr McGarrigle said. "There has been big anticipation, so it is a shame that this happened, especially at this time."
Mr McGarrigle has been targeted before for his work with the police. His car was petrol bombed in the car park of his school in 2003. He has also been the victim of numerous hoaxes.
The NASUWT is the largest teachers' union in Northern Ireland, where it has 16,000 members. The conference highlighted various problems for Ulster members, including the fact that they are not eligible for so-called "golden hello" payments if they teach shortage subjects in England.
The bonuses of up to pound;5,000 are available to English and Welsh teachers, as well as all other EU-trained staff. The exemption for Northern Ireland has outraged teachers in the province, where falling rolls mean only one in five can find permanent teaching jobs. Grainne McCay, who took out a student loan to train at Queen's University, Belfast, and now teaches information technology in Kent, was refused a golden hello.
"It is discrimination," she said. "English schools know they can get very high quality graduates from here, yet they won't give us the same incentives because they know we have a surplus. It reflects the attitude that we are just a small, forgotten province that no one really cares about."
Ms McCay directly confronted Alan Johnson, the Education Secretary, about the matter and he said he would look into the issue further as he understood the "perceived injustice".
NASUWT's Ulster members also complained that the workload agreement did not apply to them.