If your rabbit has shown grass-grabbing behavior and then after a day or two it is gone, this could be due to a number of reasons. For example, the rabbit may have just temporarily lost interest or focus. Or, it may have finished building its nest, so it doesn't need to gripe for grass anymore.

If you're concerned about your rabbit's health, you can check its diet, behavior, and physical condition to make sure there's nothing wrong with it. If you notice any unusual symptoms, such as loss of appetite, mobility problems or pain, you should seek veterinary help immediately.

In short, it's important to keep an eye on your rabbit's behavioral changes to ensure its health and well-being.