missing feeLimit in created offer data
To void a non listed offer, we need to give the complete full offer structure as it was passed when creating the offer, including the feeLimit value.
However, the feeLimit value is not returned by the protocol when the offer has been created. This value is not store in the subgraph and can't be retrieved after the offer has been created, unless the offer creator has memorised it or unless the createOffer transaction data is retro-engineered.
A solution would be to add the feeLimit in the OfferCreated event parameters, so that the value can be captured in the subgraph. eg. adding a "feeLimit" field in the OfferFees structure would allow to, both: return the value in the OfferCreated event AND in the getOffer() method