Nice, this looks so much less hacky than going through sampling (as I proposed earlier)!
Now, curiously, the two approaches give different parameter orders.
julia> DynamicPPL.syms(DynamicPPL.VarInfo(m))
(:σ, :μ)
julia> ch = sample(m,Prior(),1); ch.name_map.parameters
2-element Vector{Symbol}:
:μ
:σ
Which of the two orders is relevant for the parameter initialization in your initial post?