Word meaning existing only in the present? [duplicate]

ephemeral
But because of the ephemeral nature of television news in the 1940s , that rediscovery is not possible since those broadcasts could not be recorded. (source)

transient
The transient nature of television programming and the loss or inaccessibility of original program material make thorough analysis of specific programs, series, formats, and genres difficult. (source)

transitory
…the instantaneous and transitory nature of radio in the days before recording capabilities were widespread… (source)

impermanent
I joined WFMU & loved the transitory, impermanent nature of radio even more than I did the printed page. (source)

fugacious
…how fugacious radio reporting is: a radio broadcast can be missed, not so a book. (source)

fleeting
Unfortunately because of the fleeting nature of radio news, it was impossible to review what had been said and what precisely had been its effect. (source)

flitting
They are happy in their earthly gladness, satisfied with their human ambitions, unaware meanwhile of the flitting nature of this world and of the eternal stability of the spiritual world. (source)

passing
And then, we are reminded of the fragile and passing nature of human life and we recall that we must always be ready to greet Christ our Lord. (source)

unenduring
There is no greater delusion than to impress on people the unenduring nature of earthly things that on earth we live up to a certain period of time… (source)

evanescent
Because of the evanescent nature of radio, action and events unfold in the moment; there is no 'rewind' function or visual staging prior to sound. (source)

volatile (in the sense of 'difficult to capture or hold permanently : evanescent, transitory'; see here)
short-lived
the volatile, short-lived nature of radio broadcasts (source)

fugitive (in the sense of 'being of short duration'; see here)
We regularly hear laments about the fugitive nature of television product and the fact that we lack sufficient archival material to enable detailed histories of Australian television to be written. (source)