Jim,
I'm not familiar with a
Trillium, but most trailers have the
VIN on the left (street) side of the tongue. Our
Casita has a sticker on the street side behind where the frame goes under the shell and down low on the shell. Some times it's on the top, but more often on the side of the frame. Hopefully it is not painted over. On older trailers the label was rather fragile with inked on numbers which disappear easily when trying to clean them. Newer labels usually have the numbers raised above the surface so the tracing paper/pencil rubbing method will be revealing if the original ink is gone.
& the search continues....,
Kurt & Ann K.
P.S.,
Let us know what you discover!