Gaseous form makes you resistant to nonmagical damage and keeps you from falling
The Potion of Gaseous Form has the following description:
When you drink this potion, you gain the effect of the gaseous form spell for 1 hour (no concentration required) or until you end the effect as a bonus action. This potion's container seems to hold fog that moves and pours like water.
And the gaseous form spell description states:
You transform a willing creature you touch, along with everything it's wearing and carrying, into a misty cloud for the duration. The spell ends if the creature drops to 0 hit points. An incorporeal creature isn't affected.
While in this form, the target's only method of movement is a flying speed of 10 feet. The target can enter and occupy the space of another creature. The target has resistance to nonmagical damage, and it has advantage on Strength, Dexterity, and Constitution saving throws. The target can pass through small holes, narrow openings, and even mere cracks, though it treats liquids as though they were solid surfaces. The target can't fall and remains hovering in the air even when stunned or otherwise incapacitated.
While in the form of a misty cloud, the target can't talk or manipulate objects, and any objects it was carrying or holding can't be dropped, used, or otherwise interacted with. The target can't attack or cast spells.
It severely limits your ability to interact with your environment while in that gaseous form, but correspondingly, it also protects you from some of the negative effects of having a solid form. You have resistance to all nonmagical damage (e.g. damage from being hit by debris), and you also have advantage on Strength and Dexterity saves (e.g. to avoid being hit or pushed by debris).
So, depending on how your DM would have ruled the fall and how it might have damaged had you stayed and not used the Potion of Gaseous Form, the potion might have protected you from the worst effects of the collapse if you had stayed and used it.