In theory price v demand. Prices would increase until demand was reduced to the point that there was enough seed for everyone willing to pay the price.
It also depends whether you’re trading future that settle for cash (you buy for 5k and they give you 20k cold hard cash) or whether they’re actually going to send a semi truck to your farm, in which case they should have been holding enough collateral for such an incident.
Realistically, I believe most futures are cash settled and you’d probably be better off pocketing the extra 15k and spending 5k on planting a different crop this year.