A proposal is listed only when (1) its delivery method is a venue, (2) its status is one of the Event Status to Include statuses (default Fully Paid or Partially Paid), (3) at least one payment is recorded on it, and (4) its event date is inside the Begin/End range. A signed but unpaid proposal is therefore not shown with the default setting. Change Event Status to Include in Catering Settings > Proposals tab > Reports if you want signed events to appear, and record the deposit on the proposal.