Well, on my track, the nails hold it in place, 'cause that's how I put the track down originally. I could go back and take all of the nails out, and the track should stay where it is, because the ballast will prevent it from moving laterally. In this photo, the nails are pretty obvious:
And in this one, not so much so:
I think that it would be possible to manually lift the track, although because the ballast (and glue) in most areas is level with the tie tops, it would be a bit more of a task. The white glue still isn't "gluing" the track in place, but the surrounding ballast, which
is glued to the cork, helps hold the track in place through friction. I'm surprised that wetting the area would cause your track to pop loose, though, unless, when you originally "glued" it in place, you had to place weights on that section until the glue dried. If the track was laying there naturally before you glued it, even if the alcohol/water dissolved all of the glue, I can see no reason why the track should have moved.
Did you previously have any problems with derailments or rough running through the area where the track popped loose? If so, there may have been a "kink" in the track just waiting for an opportunity to move, or, as I said, if you had to somehow hold that particular track in place while the original glue dried, then there is a track problem there that should be corrected while you have the opportunity. If none of the above is the case, then you could use a few nails to hold the tracks in place while you do the ballasting. I used Atlas track nails, and Peco and Model Power make similar nails. Most track has preformed holes every 6" or 8", although with some brands, they're visible only from the bottom, and require you to push a nail through from that side to open the hole completely. If no holes are visible, use a drill bit just slightly larger than the diameter of the nails that you intend to use, and space the holes accordingly. It's not necessary to place them all halfway between the rails, either, although most commercial track has them that way. Use pliers to push them into place, and don't push them right down to the tie tops - as close as you can get, but not so close that they squish the tie, which will then pull the rails out-of-gauge. You can paint them, let them "weather" on their own (most come pre-blackened), or pull them out after your ballast has completely dried.
What would happen If I didnt glue down the ballast, I mean that way I could reuse it on another layout. It can get expensive, and this layout will need alot, I might never need to buy it again.
Ballast really isn't
that expensive

: I think that I used only 4 or 5 cannisters of the Woodland Scenics ballast to do most of my layout, and I used it as fill in some areas, where it's over an inch deep. I also did roads and parking lots with it, too.
If you don't glue the ballast in place, it will eventually work its way into your turnouts, loco mechanisms and who-knows-where, plus, when it comes time to vacuum your layout, (and that time eventually does come - it took over 15 years for my layout), but re-ballasting everything would've been too onerous a task, even though I do find it to be otherwise enjoyable work.
Wayne