Recently, I was visiting a famous town in Israel known for its religious adherence. I walked into a local pizza restaurant and was surprised to find that there was no te’udat hechsher that I could see. When I asked the the man working there (who may or may not have been the owner) if the shop was kosher, he mocked my question.. When I showed that I was serious, he informed me that his food is kosher, but that he does not have any te’udah and was not under the supervision of any Rabbinic authority. He said that since he and all his customers were "chareidi," it was obvious that the shop was kosher. However, other customers in the shop who heard this conversation were also shocked to discover that he did not have any te’udah whatsoever - it just never occured to them to ask. I decided not to eat there. Was I being too stringent? Is it permissible to eat in a public establishment, where you don’t know the owner, based solely on the shop’s own declaration that it is kosher?
One cannot trust a store without certification. They are doing business. You were not too stringent. Nowadays, with the Kashrut situation as it is, there has to be at least a Rabbinute Hechsher, otherwise the place is highly questionable. Rabbi Yosef Weitzen