Many shop vacs will vacuum up water, if you remove the dust filter. They tend to be pretty cheap and are useful for spills.

Oh yes, I used shop vac to vacuum up the water off concrete after removing the planks. And then set up floor fan and dehumidifier. But still worried about the planks under the appliances and water heater. I'd rather not take any chances with mold.

I think there are three standards here.

1. What you need to do to be reasonably sure it's not going to mold.

2. What is reasonable to ask of your contractor.

3. What is going to make you feel like enough has been done.

The answer to number one and number two are to remove the accessible planks and vacuum up any liquid water. Then run a fan and dehumidifier.

We can't really say what would be enough to make you feel like enough has been done.

This is not the contractor's problem.

It's good you worked to stop the problem the minute you discovered the water.

When it comes to plumbing there's going to be water. If you dry the area out, pointing the fans directly at the flooring under the water heater I don't think you'll have an issue with mold unless your basement has a humidity problem.

Most in the house water heaters have leak pans. Perhaps yours did and water escaped anyway. It's very probable to have some leakage when changing out a water heater but usually not more than escapes a pan unless the water heater is rotted out. If you don't have a pan, have one installed the next time you replace it. https://www.killarneymetals.com/categories/water-heater-pans

The key to what to do from here is "(I don't really want to put the planks back in and would rather just have bare concrete in case of future water issues - "

I tend to agree and would lift heater and remove flooring. Whether it results in mold or not, it will look like sh*t if left in place.

Vinyl planks are the correct choice for this situation. In coastal areas near me, insurance companies have stopped insuring hardwood floors due to having to replace them after water damage. The preference is vinyl flooring because you can pull it up, let it dry and then replace. Let the area dry, you should be fine unless it is a damp basement all the time.

You probably have a damp basement. Uncap the concrete and water proof it. You will need to install sleepers and wood subfloor to lay any other type of flooring in the future. The air gap will help dry out any moisture.

Vinyl floors have to be replaced after floods too. Because just removing it damages the click. It's a much bigger issue for water damage to substrates as well, because it's vapor impermeable. Because of condensation, mold tends to grow under it whether or not you have an actual physical leak or not. It's all bad news directly on any concrete slab.