The feeling of forgetting something that you just remembered is commonly referred to as "tip-of-the-tongue" phenomenon or "presque vu" (meaning "almost seen" in French). It's a frustrating experience where you know that you know something, but you can't recall it at that moment.
During the tip-of-the-tongue state, you may have a strong sense of familiarity with the information you're trying to remember, and you might be able to recall certain related details or characteristics, but the specific piece of information remains temporarily inaccessible. This phenomenon is quite common and can happen to anyone.
Various factors can contribute to this feeling, including the complexity of the information, interference from similar memories, stress, fatigue, or simply the passage of time since you initially learned or encountered the information.
Fortunately, in many cases, the forgotten information eventually comes to mind with a little more time or after a change in thought processes or context. Trying not to focus too intensely on the memory and allowing your mind to relax can sometimes help the information to surface naturally. Additionally, distracting yourself with other tasks for a while can sometimes lead to the "aha!" moment when the memory resurfaces.