A list with only one item

Solution 1:

Speaking as a programmer, no. A list can even contain no items at all.

Edit: on a more serious note, let's say I take a piece of paper and a pen, and make my grocery list. And then it just so happens that all I need is milk.

That piece of paper with a single word on it would still be my grocery list, and not my grocery word.

Solution 2:

Sounds like you are getting hung up on semantics.

Sure, it may not technically be a "list" at that point, but unless you are referring to it as such in the narrative, why fight it? I mean, it is just a formatting element at that point and technically not a grammar issue.