Suffocated Forever is a memento that can be found in Silent Hill: Shattered Memories by Harry Mason. The memento is found near the second floor exit of the Cat House, closed inside of a heart-shaped jewelry box, and is an insect trapped in fossilized amber.
The memento could refer to the way that the bug is trapped in time and preserved, much like Cheryl Mason's memories of Harry. This is also supported by the fossil being located in a heart-shaped box, which shows its owner clearly held the object dearly. This can also be a reference to Cheryl's hobbies, as Harry can tell Lisa that Cheryl is into bugs.