Equivalent model of my (real) transformer
It’s really tricky to theorize on leakage inductance given only that you have a non-looping ferrite rod. If the rod was in fact a full magnetic core you can make the assumption that all the flux produced took the path through the core. But, then, the problem would be that there can be no leakage inductance i.e. the two coils would be perfectly coupled and, when perfectly coupled, there is no leakage inductance to form a tuned circuit with the secondary capacitor.

I would suggest that you measure the inductance of the secondary with the primary shorted in order to ascertain the effective leakage inductance that would form the tuned resonant circuit.