How does it not exist? It is still commonly referenced (e.g. https://www.yimba.sk/kollarovo-namestie-revitalizacia/kollarovo-namestie-sa-moze-coskoro-zmenit, https://www.staremesto.sk/sk/proceduralcuttings/index/street:1390/section:citizen (city website)). It may be it has no addresses, but the street with the name seems to exists. Yes, all the surrounding area is Kollarovo namestie.