Does zakat become void if the giver informs the needy person that the zakat is not from him, in order to avoid embarrassment and currying favor?

It is not obligatory to inform the poor person that the money is Zakat, nor is it obligatory to inform him that it is your Zakat.

What was done does not invalidate the Zakat, but it would have been better to use allusive language instead of outright lying, such as saying, "This is Zakat from one of the benefactors."