Force majeure credit: when neither side can make the booking happen
When something outside either side's control makes a booking impossible, such as an official order stopping the journey, the deposit becomes credit.
Force majeure is the narrow case in which neither the guest nor the house can make a booking happen, for reasons neither of them controls. A transport shutdown, a serious disruption in the city, or an official instruction that makes the journey impossible are the examples. In that case nothing is forfeited. The deposit becomes credit, held against a later date that you do not have to choose immediately.
What does not count
On an event trip, a lot of things feel outside your control but are not force majeure in this sense. Crowds and road closures that were announced weeks ahead are part of planning the hour. A flight changed by an airline, an illness, a set that moved, a game that overran or a decision late in the evening that you would rather sleep all fall on the guest's side. Each is handled as a free move or a cancellation on the ordinary notice scale.
When the house cannot deliver
A separate case is when the house is unable to provide the booking you agreed. Then the choice is yours: the deposit back in full, or credit against a new date. If the woman you booked cannot come, you are told as soon as the house knows, and you can take another name from the roster or take the deposit back.