VLookUp doesn't find an exact match even though FALSE is used as the last parameter.

Hi everyone,
does anybody have an idea why VLookUp doesn't find an exact match even though FALSE is used as the last parameter?

I have two formulas:

=VLOOKUP("123","A:B",2,FALSE)

and

=VLOOKUP("1234","A:B",2,FALSE)

The first formula finds value, but the second one doesn't.
The left column ("A") is formated as TEXT and both LOOKUP_VALUES (123 and 1234) are presented in column "A".

In other words, the formulas are almost the same, except that LOOKUP_VALUES (123 and 1234) are different.

Thank you.
surotkin