I think the term "callback" makes sense in your context. Please, read below.


Call-back overtime (HHS Instruction 550-1 dated 6/12/96) occurs when employees are required to work after leaving the work site or perform overtime work on a day, or time, for which they are not scheduled to work. A minimum of 2 hours overtime is credited, even though the employee may perform no work after returning to the work site. It is possible to have several call backs in a 24-hour period. Overtime is computed at one and a half times base pay. "Call back" does not require the employee to physically return to the work site, merely to return to work status.

Because call back work is irregular/occasional overtime work, compensatory time off may be substituted for pay at the employee's request. The employee receives a minimum of 2 hours compensatory time per call back. The employee may be called back to perform overtime if it is in lieu of regular overtime.

http://090.nihweb5.cit.nih.gov/hr/hrdata/policies/callback.h...