My local craft shop offers a most helpful service of taking back unused balls of yarn, and some time ago I returned a ball of Debbie Bliss Riva in Thistle, having finished crocheting a scarf in it:
I was in the shop on Saturday (learning something rather lovely, of which more later) and the lonely ball of yarn was calling to me. So I re-bought it, and now have a cosy hat to match my scarf!
It has been quite a good experience actually as the last hat I made was very early on in my crochet journey, and I can see that my technique has come on:
Simply hooked 
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