LVT on concrete floor, fast leak flooded the bathroom. Do we need to take flooring up?

It should be fine. Use a dehumidifier to extract the remaining water to prevent sweating of the concrete

If it was a `Click` LVT, they usually have an underlay incorporated to it or are laid on an underlay. If it was a `Stick Down` LVT, you would be fine, but i would DEFINITELY recommend uplifting it, due to mould & mildew, etc, which can cause health issues. Hope this helps, Chris.

Ideally the LVT floor should be lifted to allow the concrete slab to dry out. Without this, it could cause a trapped water void between the subfloor and the LVT that could harbour bacteria and cause an awful smell over time with the possible disintegration of the built in underlay, this in turn could lead to a weak point in the click mechanism itself due to uneven backing of the product. If it hasn't been sealed yet, it's a simple un-click and refit job once dry. If you take the floor up, take it up in rows and remember each rows position and the starting point. That way each cut will fit back into its original position with no need to re-scribe. Hope this helps!

I would pull the flooring up carefully and soak up remaining water and thoughtly dry then re-lay the flooring