Hi tarpon21,
I think that dn has covered most of what I would also reply but to add a few comments …
Most of what he said is certainly funny including that only the tempurpedic is “all foam” when almost every memory foam mattress is all foam. I hope he wasn’t thinking that Tempurpedic is all memory foam which of course is nonsense.
As dn also mentioned … one thing that he did say that is accurate is that ILD is not a particularly meaningful spec with memory foam (see post #2 here) because the ILD of memory foam changes in response to temperature, humidity, and the amount of time the memory foam is compressed and it’s response also depends on how quickly it’s compressed. All memory foam has a relatively low and soft ILD so its really a matter of degrees of softness and the other properties of memory foam will contribute much more to how it feels and performs than it’s ILD.
Your only option would be to make a warranty claim and they will come out and measure the visible impressions in your mattress or check for any other defects that are covered in the warranty. They will usually charge you for the inspection. If the impressions are more than the warranty exclusion (usually 1.5") and there are no stains of any kind on the mattress and all the other terms of the warranty have been maintained then you would qualify for a replacement under the terms of the warranty (not a refund … partial or otherwise). If the impressions are less than the warranty exclusion then you would have to wait (normally 6 months) before you could have another inspector come out and measure the impressions and the process will repeat.
If the impressions or sagging is only “virtual” from foam softening that you can only feel when you are lying on the mattress and there are no visible impressions when you are off the mattress that are deeper than the warranty exclusion then there is no warranty coverage.
Phoenix