I cannot find my 2019 tax documents in my account

That's probably because the IRS is way far behind and hasn't processed it yet.  I mailed in my 2019 return in June of 2020 and my enclosed check was cashed within the week, but IRS accounts site still says I didn't file a 2019 return. Nine months and they still haven't processed it!

I assume you did not use a method where you got proof of delivery so there is no way to tell if the IRS got your return. if you call they will not have any better info if the return hasn't been entered into their computer system.  at the end of February 2021, it had over 7 million returns it hasn't processed.  the IRS prefers that duplicate returns not be filed. it's your decision if you go ahead and send in a second copy. if you do you should use a method where you get proof of delivery.