As a general rule, Delay Repay only applies for journeys that were actually made.
However discretion may be shown for Season tickets (for single or return tickets you would get a full refund in your situation whereby the ticket would be wholly unused)
I had a quick look for Scotrail's policy on the matter but it wasn't immediately obvious to me what their policy is. I am sure someone else will know...
I'd argue that it would be reasonable for you to be given a pro-rata refund of £5.50*. Whether it's worth the hassle of completing the form for such a sum I'll leave up to you. (* The ticket is valid for 7 days but it's reasonable to assume 5 days usage) and it's not clear to me if that would be Scotrail's policy, or whether you'd fill in a Delay Repay or a refund form (I'd assume the latter given you didn't make the journey).