It's possible for a stronghold to generate with incomplete or missing frames, making them inoperable. For that reason there have always been 3 strongholds that generate per map, even in Bedrock edition, and that number was increased to 128 in 1.9 for us java players. While I'm sure you did in fact find a stronghold with no portal I'm sure one of the other 127 in your seed will have an intact one: just get some more eyes and get hunting again.
The location given seems to be most consistent with the seed "1989659868" in 1.6-1.8, where ChunkBase shows a stronghold at 996, 468 in 1.6 and 964, 468 in 1.7-1.8, which are both close enough to be the correct one (strongholds can extend up to 112 blocks from their starting point, which in turn can be up to 112 blocks from the initially chosen location). Otherwise, all the strongholds in 1.9 and later are way too far away.
Also, 99% of the time when somebody claims that there is no portal there actually is one; the only time one will not exist is if a generation error occurred or the world was upgraded form an older version and the stronghold straddled the chunk boundary between version changes, otherwise, I've never, ever seen this myself, even across countless test worlds when testing mods (as I use tools that let you see everything underground, including strongholds, which stand out). It used to be possible that they would be overwritten by other structures, at least mineshafts, but that was fixed long ago by making strongholds generate after them*, and caves/ravines can't ever overwrite them* because they are terrain, not structures (this is like claiming that the air above the surface can overwrite structures. Strongholds lack walls where they intersect air only because the generator ignores air blocks, but everything inside generates, as seen on a void Superflat world; the portal room (seen near the top-center) is also always fully intact, even underwater, which prevented everything else from generating prior to 1.13, and dungeons can still possibly generate over a portal room, but you'd still be able to recognize it.
*The seed "-123775873255737467" in 1.6.4 (my own world) has a portal room near 30, -550 which is intersected by both a mineshaft and a ravine - and is fully intact; indeed, you can see I dug down to it and activated the portal to go to the End:
(interestingly enough, ChunkBase shows that this stronghold is at 20, -556, or 556 blocks from the origin, which seems to violate the minimum distance of 640 blocks (prior to 1.9) but that is because the game relocates them up to 112 blocks from the initial location if the biome is unsuitable, so the portal room can actually be up to 224 blocks closer or further than the initial bounds)