You won't catch everything but I've found if you specify that it's okay to respond that it doesn't know the answer and essentially accuracy on a smaller subset of answers > responding to all, it often will say it doesn't know rather than making something up.

Another option could be - assuming this is an LLMChain that adds the most similar (n) embedding(s) to the prompt before passing to LLM - basic entity recognition to find the asset name from the query initially and dynamic prompt that if the most similar results don't contain the asset name, don't provide examples and respond saying you don't know.