IF function with ISNumber(Search()) and Vlookup

Hi!
I am trying to write a function that would use two vlookups, where in the first vlookup there are also IsNumber(Search()) supporting it. What I have written looks like this - IF(ISNUMBER(SEARCH("part of text", d3)),VLOOKUP(D3, 'tab x'!A:B,2,false),VLOOKUP(D3, 'tab x'!A:C,3,FALSE)).

As you can see that in the first Vlookup, if cell D3 starts with certain text then we use data set of A:B. If D3 doesn't start with the needed text, then it is false and the second vlookup performs the search for cell D3 in the A:C dataset. Unfortunately, the function doesn't return what I need, however before I had those functions separately and they worked. It would be great if there is a solution to combine the two.

*I also tried IFERROR instead of IF and it didn't help

Thanks a lot!!