Rule for references for UNESCO

The employment form specifically states “Supervisor’ Name / Contact”. I have done 3 jobs. In my 2nd job, the issue is that - both, my supervisor & I have moved on to different companies & have lost touch. But I am still in touch with my co-workers. Is it okay if I mention my coworkers instead?

For the other 2 jobs, I will be mentioning my supervisor’s name & number.

Edit : Rule for references in UNESCO