Could a I-829 denial cause me to loose my H-1B status?

An I‑829 denial does not “take away” H‑1B status, because by the time you file Form I‑829 you are already a conditional permanent resident (a green card holder), not an H‑1B nonimmigrant.

If you need to file I-829, you should have a conditional green card and your H-1B should not be used because you can't keep your non-immigrant visa or status while you are a conditional permanent resident.

Once you get your conditional residence after I-526, an either I-485 or immigrant visa approval, the H-1B ends. To get back into H status after I-829 denial you would need to take an approved H petition overseas and re-enter with H visa to be back in that status.

Before you can file an I-829, you must be a conditional green card holder for 21 months.
Once you a conditional green card holder, you not on H-1 nonimmigrant status but if your I-829 is denied, one of the things you can do is surrender your green card status and then apply for an H-1B abroad, provided you have less than 6 years of H-1B status or qualify to go beyond 6 years of H. a new wrinkle is that the $100,000 H-1B fee may apply.

When it is time to file I-829 you would have already been a permanent resident of the US, therefore your H1-B status would be null and void.