Date : ____________
[NAME, COMPANY AND ADDRESS]
Dear ________ [NAME, ex. Kelly],
I just wanted to send you a short not thanking you for taking care of my files while I was on vacation.
I know how stressful your own workload is, and I can appreciate that by carrying my additional workload, you probably had very little free time last week.
Again, I’m very grateful for what you did, and I would be happy to reciprocate whenever you feel you need some time off.
[YOUR NAME, ex. Jones]