Research methods

Oct 2020
Hanoi, Vietnam
Hi, great to be a part of this forum.

My tutor has asked me to justify my sampling method for a study into cued & uncued recall. But it doesn't sound very scientific to say 'constraints of time and budget', which is the reality. I used opportunistic sampling method - I basically asked the sales team at my workplace at to do it. But in all the studies into CR & FR I've read, no researchers feel the need to justify their sampling method. They just explain it. So I've no example. No basis. Also, the study title I was given doesn't define a target population! It could just be memory for....anyone.
What do you think? How can I make 'opportunistic sampling' seem like to appropriate sampling method in this case?
Any advice much appreciated!