SOLVED !!
I worked with Apple support team and finally got a resolution.
The stocks app is set up to sync with iCloud on both your iPhone and iPad. (usually)
This setting can be found under Settings > [Your Name] > iCloud > Stocks.
If it’s turned ON for both devices, you’ll want to "delete" the Stocks app from your iPhone, then restart your device and download it again from the App Store afterwards.
Once Stocks is reinstalled, ensure that the option to "sync" with iCloud is turned ON,
this brings back your original watchlist back on the Stock app on your phone.
SOLVED !!!
(mark "this solved my question", if this solution indeed helps your case.)