Help needed to find someone!

I wonder if anyone can help me. I lost touch with a Bulgarian national. I have part of her address, and sent a letter. Some time later the letter was returned with a stamp indicating "insufficient address"
The address format I have is :

Инна Завалишина
Meчка
Улица Царь Борис 3
Третий/55
Bulgaria

I'm now aware of the postcode 5843, but is there something else missing or incorrect!

Thanks
Jack

Pretty sure it is mainly complete but some call it Село Мечка in the Pleven region , you could try
Инна Завалишина
Село Meчка 5843
район плевен
Улица Царь Борис 3
Третий/55
Bulgaria

also ask on facebook on living in Bulgaria page