Can a seller be forced to disclose something that isn't technically required by a schedule?

In a practical sense, yes, though it doesn't usually work as a single blanket demand — a seller's overall disclosure obligation in a purchase agreement is typically broader than just what's physically listed on the named schedules. Representations and warranties in the body of the agreement often require disclosure of anything material to a given topic, whether or not it fits neatly into a pre-defined schedule category, and many agreements include a general, catch-all representation requiring disclosure of anything else material the buyer would reasonably want to know.

Due diligence itself is the other lever — a buyer isn't limited to what the seller volunteers in the schedules; it can ask direct, specific questions, request documents, and require answers as part of the process, and a seller who withholds a direct answer to a direct question faces real risk if the omission later surfaces. Separately, some agreements include an express seller representation that the schedules and disclosures provided are complete and not misleading, which itself creates an independent obligation beyond the individual schedule entries.

If you suspect something material hasn't been disclosed, raising specific, pointed questions during diligence — and getting the answers in writing — is often more effective than waiting to see what appears on a schedule.