I don't think supervisor's name and details are a requirement for the letters.
IRCC states that letter need to have 'the name, title and signature of the immediate supervisor or personnel officer at the company',' Note the 'or personnel officer' (a.k.a. HR) portion. Essentially, they just want the name of someone to call to verify the letter if needed (although I understand that verification by calling these people is rare).
So as long as an authorized person signed your letter (someone from HR, or a supervisor's supervisor, or a department manager, or Company executive, or something like that), lack of a supervisor's details shouldn't be a problem.