Odd behaviour after disk conversion (partition disappeared)

Hi,

I have a virtual machine on Hyper-V running 12.1-RELEASE-p2. Root is
mounted on /dev/da0s1a. Now we have converted the disk image from .vhdx to
.vmdk to use it on a VMware workstation. Now the BSD partitions
disappeared, but the thing still boots, but from /dev/ada0s1. Of course I
cannot see the swap partition anymore.

gpart show da0 on the old image shows:
=>      63  62914497  da0  MBR  (30G)
        63         1       - free -  (512B)
        64  62914495    1  freebsd  [active]  (30G)
  62914559         1       - free -  (512B)

and gpart show da0s1:
=>       0  62914495  da0s1  BSD  (30G)
         0  58720256      1  freebsd-ufs  (28G)
  58720256   3145728      2  freebsd-swap  (1.5G)
  61865984   1048511         - free -  (512M)

on the new image gpart show ada0:
=>      63  62914497  da0  MBR  (30G)
        63         1       - free -  (512B)
        64  62914495    1  freebsd  [active]  (30G)
  62914559         1       - free -  (512B)

and gpart show ada0s1:
gpart: No such geom: ada0s1.

What happened? The conversion process is supposed to make a 1:1 copy of
the disk image.

Cheers,
harti