Replacing a diode-OR gate by a circuit that behaves the same way (also in the presence of feedback loops) without accumulating voltage loss
Consider your diode circuit: when the inputs are both zero volts, where would the energy come from to maintain an output at anything other than zero volts?

The "real" or "traditional" OR gates have an implicit supply voltage that will maintain the state of the outputs. Simulation tools sometimes "handwave" this away so as to not clutter up the schematic with unnecessary supply connections.

Consider the following circuit diagram representing a traditional CMOS OR gate implemented with transistors:


In this circuit, the circuit elements that comprise the OR gate are powered from VDD, and thus can provide power to the output Q. In your diode circuit, there is no such power supply, and thus no latching, or as you put it, memory.