Some mileage partners insist that LH sends them some proof, some don't. When I signed on my GF (now wife) on M&M, we sent in SK ticket copies and baggage stubs in (no BP, same case, she had to give it to her employer) and LH credited everything.

In other cases (SQ is particularly famous for this) LH came back after 3-4 weeks to state that the partner airline declined to credit due to missing documentation.