My employer sent me the H1B rejection notice, which has a receipt number on it and which states H1B application wasn’t picked up in lottery. Can we check the validity of this receipt number on rejection notice ?, just to make sure it is a legit rejection notice, not like my employer modified any rejection notice and sent it to me.
Sorry to hear that, but you can believe your employer.
You can ask for rejection notice, but there is no point of it. If you think employer have lied you, then they can modify the docs and can send you.
My suggestion, believe them and try some other options.