I mean, the Defiant had internal nacelles. other (alien) ships had internal nacelles. or even just “Warp field maintenance coils” that would allow them to sustain warp until they got far enough away or someplace habitable. But I doubt very much the Saucer would be able to reach someplace safe just carried by “inertia”. particularly because the warp drive doesn’t seem to actually be the ship moving. (once the warp field collapses, the ship is dead in the water.)