Whether we can refund you if a return gets lost depends on how you sent the parcel.
Through our return portal, label scanned at the drop-off point
From the scan onwards the parcel is our responsibility. We open an investigation with our return partner and the carrier. We sometimes need something from you for that, such as your drop-off receipt; our return partner may contact you directly about it. Your refund comes regardless, even if the parcel never turns up.
Through our return portal, but the label was never scanned
Without a scan there is no proof that you handed the parcel in. The parcel then counts as not sent, and we cannot open an investigation or refund you. So always have your label scanned and ask for your drop-off receipt.
With your own carrier, outside the portal
Then the parcel remains your responsibility until it has arrived with us. If it gets lost, you contact your carrier yourself. We refund as soon as the parcel has reached us, or as soon as you have shown that you sent it.
In short: use the portal and keep your drop-off receipt, and you are covered.