@arunava_chakrab have you check if there is any cron running which is deleting the products.
Also please check the database if you get any clue from there.
Thanks
Do you have Magento code in version control like Git / Bitbucket etc? Is same thing is working properly in staging than deletion should not be happening in the Production. There can be various reason I can think of. This is definitely a coding/coder issue.
Following things can be checks:
1. Do you have a delete query hard coded somewhere?
2. Staging DB user have delete permission? Possibly production has...
3. Someone manually did it without realizing it? It is possible and I have seen this personally. From product list screen instead of selecting visible all on the page user have selected "All" and deleted all products.
4. Are you on Commerce or Open source version? If commerce then you can look into admin logs.
5. Ask you developer if they have some unbaked code checked in.
Nothing happens all by itself unless it was meant to do that.