Stay relaxed.
It is not uncommon that there are plans for plots of land, but the subdivision is only commissioned when concrete buyers are available. This means that the plot cannot yet be seen on the cadastral map and therefore cannot yet be purchased.
Nevertheless, it is possible to draw up and conclude a purchase contract, which is then implemented step by step. The (to scale) plan is then attached to this purchase contract and the object of purchase is described, for example Plan plot 12, size approx. 600m². The plan can/should also include approximate plot dimensions (here: approx. 20x30m or similar). The surveying office commissioned then forms the plot according to these specifications and the new boundaries must then be acknowledged by the seller. Usually, the buyers are also present at the boundary appointment; they can also act as clients/cost bearers.
The advantage is that the plots can possibly still be adapted to any wishes of the buyers and that the investors/developers of the building area do not have to advance the entire surveying costs for all plots.
Best regards Dirk Grafe