Got it too !
I was stuck with symetry problems, why is f6 different from d6 for the king ? and since the queen has to be defended by d4, why does the queen have only one way to reach e3? she can go by d3 or d2 ...
but since you had found it i had to find it too! and your hint helped : i looked for unusual solutions and quickly reached the light of truth of the vedas (as dasa would say)
And i like your other solution too. Yuo solved this one twice !
I like my other solution too but it's not pure in the problem sense
as it can be reached via a different move order.
1. d3 d6 2. Kd2 e6 3. Kc3 Qd7 4. Kd4 Qc6 5. e3 e5 mate.
The real solution, like all good problems has only one move order.
The solvers 'trap' was I think a piece going from e3 to e5.
This had me looking for discovered checkmates.
But no luck there.
I then thought the board might be upside down/sideways.
Too low a trick for SG but he did say it was me and Adram so looked
for sneak shots.