i did the exact same thing last summer and they took forever to refund me, told me for a while that the package must be lost, then a couple of weeks after refunded me without notice. i'd keep on at them to look for the package, seems like they're very disorganised.
same happened to me a couple of years ago…thought they'd upped their game tho as this year my returns were processed quickly
nice one, will keep on at them. said they havent received it as of today and i posted early Jan. my fault for no tracking but i wonder if they try it on a bit when they know parcel isnt tracked (i havent told them this however)