Why isn't current through D2 0 in LTSPICE?
without running your circuit to check, it is usual to expect leakage current in bipolar devices, and silicon diodes are p type and n type, hence the bipolar name. When one diode is reversed biased, impurities in the silicon structure allow a very small current to flow through the device. This current is very temperature sensitive. In a circuit such as this I would expect the reverse bias leakage current to be micro amps or less.