The Scottish Secondary Teachers' Association (SSTA) said the incident was one of a number that highlighted a recent shortage of supply teachers.
The SSTA also said there were cases where staff employed to look after pupils with special needs were drafted in to provide supply cover.
The shortage follows a deal drawn up by the Scottish Government and council body Cosla last year, in which pay rates for supply teachers were reduced as part of wider cuts to save councils £45 million.
It means short-term supply staff must work at a rate of £78 a day for their first five consecutive days in employment before their pay rises to the normal rate of £145.
Councils have been accused of deliberately keeping supply work to less than a week in some cases to avoid paying the higher rate.
The Government said the deal was the best that could have been done and it protected frontline teaching jobs.
However, a subsequent survey by the Scottish Labour Party found 84% of councils did not fill all requests for short-term cover in 2011.
Alan McKenzie, acting general secretary of the SSTA, called for the "derisory" pay rate to be ended and proper salary rates restored.
"These reports may only be anecdotal, but we believe there is a problem derived from the introduction of the lowest rate of pay for supply staff," he said.
"Very few experienced and recently retired teachers are prepared to accept supply posts on the daily rate currently offered. We are also alarmed that many newly qualified teachers are simply leaving the profession when faced with long periods of second-rate payment."
John Stodter, general secretary of the Association of Directors of Education in Scotland, said the issue was partly because many more staff were securing full-time jobs.
Recent figures showed employment rates for newly-qualified staff are now better than at any time since 2006/07 and teacher unemployment is lower in Scotland than anywhere else in the UK.
The study by the General Teaching Council for Scotland found the proportion of probationers who find permanent employment is now 35%, up from 21% last year, while there has also been a rise in the proportion of new teachers securing part-time permanent jobs and full-time temporary contracts.
"There are clearly problems in the availability of supply teachers for short-term work and this is directly related to the record numbers of teachers now securing longer-term employment," said Mr Stodter.
A Scottish Government spokesman said: "We are providing stability in classrooms and teacher employment is higher in Scotland than anywhere else in the UK.
"The numbers of teachers trained each year includes an allowance to ensure there is a pool of supply teachers.
"The Scottish Negotiating Committee for Teachers is currently monitoring supply issues and we will play our part in those discussions."