Hello, and welcome!
Even though you're a Precheck member, it's a randomized system and you won't always be chosen to receive it on every flight. Yes, it is recommended to have your number included in your profile with all the airlines you fly frequently and if your travel agent handles this for you, s/he should have the number to include with your reservations.
To retrieve your KTN (Known Traveler Number) from TSA Precheck, go to the following site and enter the required information:
You can also call Universal Enrollment Service at ***-***-****.
I hope this helps!
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