I put a coin into a gumball machine (which I assume was owned by a Jew since it was in a kosher restaurant) to buy a gumball, and the machine got jammed. Am I required to find out who owns the machine and pay him for the damage and/or the losses he incurred while it was broken?
You are not obligated to pay for damages. The machine is there to be used (the owner gives his “permission” for anybody to “use” it), and as far as I understand you did nothing beyond the normal “use” of the machine, namely putting a coin though the appropriate slot. Because your use of the machine was normal and with permission, you are exempt from liability for any damage caused.