I took $ from 401K when it was offered with no penalty. I paid tax prior to receiving check. 1099-R not received. should I have?

Yes.  A 1099-R for any  2020 401(k) distribution was required to be sent to you no later than Jan 31, 2021 and MUST be on your 2020 tax return.  If not, then you will receive a big bill from the IRS and the tax paid will not be credited to you.

Contact the plan administrator for a copy - it might have been lost in the  mail.

Yes ask them for the 1099R.  Maybe you can log into your 401K account and get a copy.  They should have them online.

If you made a withdrawal from the 401(k) in 2020 then you should have received a Form 1099-R from the plan administrator in January 2021. 

If you did not receive the 1099-R then you need to contact the plan and get the 1099-R either mailed to you or it may be available on the plan website.