Completeness is one of the most important attributes of software requirement specification. Unfortunately, incompleteness is one of the most difficult violations to detect. Some approaches have been proposed to detect missing requirements based on the requirement-oriented domain model. However, these kinds of models are actually lack for lots of domains. Fortunately, the domain models constructed for different purposes can usually be found online. This raises a question: whether or not these domain models are useful for finding the missing functional information in requirement specification? To explore this question, we design and conduct a preliminary study by computing the overlapping rate between the entities in domain models and the concepts of natural language software requirements, and then digging into four regularities of the occurrence of these entities(concepts) based on two example domains. The usefulness of these regularities, especially the one based our proposed metric AHME (with 54% and 70% of F2 on the two domains), has been initially evaluated with an additional experiment.