It hasn't disappeared. You need to tell Calendar the location of the event and where you are, although this can be automatic - see below.
You didn't state which device you are using.
On a Mac your location is determined by several settings described by Apple in Add location and travel time to events in Calendar on Mac:
Calendar finds your starting location by using the location in any events that are up to 3 hours before this event. If Calendar doesn’t find a location, it uses your work address or home address (from your card in the Contacts app), depending on the time of day. (Set your work hours in Calendar General settings using the “Day starts at” and “Day ends at” pop-up menus.) If your card in Contacts doesn’t have your addresses, Calendar uses your computer’s current location. Determining your computer’s location requires Location Services to be turned on (see Change Privacy settings).
In iOS create a new event, add its location, touch on Travel Time, toggle it on, then select your mode of transport.
The same rules apply as with a Mac calendar event with regard to prior calendar events and the point of departure.