Hello -- First, as you may know, IBC discontinued its operations in early 2012. So my presumption here would be that this question relates to a mattress you purchased before then, rather than one you are looking at purchasing now.

Assuming this is correct, your best bet since you didn't keep a copy of the warranty is to go back to the retailer from whom you purchased it to find out the terms of the warranty. You will be at their mercy anyway in terms of the upholding of the warranty, since the manufacturer that actually offered the warranty in the first place no longer exists.

As an additional note, I'd recommend you be as polite as possible when approaching the retailer about this. Chances are that they have no legal obligation to offer you anything under the terms of the warranty (since warranties generally come from the manufacturer, not the retailer). So your hope is that they will value you enough as a customer to help you anyway, and that perhaps they will want to take this as an opportunity to set themselves apart from other retailers by going above and beyond the call of duty with their customer service. If in the end they do prove willing to help, you can return the favor by coming back here and writing them a glowing review that will win them other customers in the future.

Hope that helps.