I've had that happen a few times over the years....but actually never swallowed any water....as soon as I began inhaling, the density difference of the water let me know that "something" was wrong, and I stopped inhaling. Actually, most mouthpieces fit fairly tightly even without a ziptie, so I just put it back together & continued the dive. (got a new ziptie later) I guess I wouldn't really recommend doing that, if you're at all concerned about it happening again...could always use your octo instead, but then you'd be without a completely reliable alt. air for the rest of the dive.
I had another funny thing along the same line happen to me once....my mask suddenly flooded & I tried to clear it. I COULD NOT clear it, and I NEVER have any problem with that, or swimming without the mask, etc. Took me a second to figure out what had happened....one of the mask LENSES had fallen out, ha ha. Pretty hard to clear in that situation!