I reported a 401k withdraw on one 5b and think it should have been line 16a. Could this help me if I do an amendment?

What year is it?  401K should be on 1040 line 5b taxable and 5a gross.  There is no line 16a.  Line 16 is for the tax.  But the 1040 lines have changed over the years.  Probably a prior year it was on line 16.  

Way back in 2017 pensions and 401K were on line 16.  Then they started changing all the line numbers in 2018.

This was on my 2022 tax returns.  We withdrew from our 401k to purchase a property but it fell through.  So of course we were taxed as income.  This put us in a different tax bracket.  An advisor mentioned I may have put it in the wrong spot.  I wondered if I did and if doing an amendment may get some of my $14k back

Sorry line 5b is right for  2022.  It is all taxable and there is a 10% early withdrawal penalty if you were under 59 1/2 on schedule 2 line 8 which goes to 1040 line 23.  Sorry.  No you can't amend and get any back.  

You paid 14,000 tax?   How much was the withdrawal?  Did they take any taxes out of it (that should be on 1040 line 25b)?  Did you put any of it back into the 401K?  You had 60 days to return it so it wouldn't be taxed.