Sorry, you are right!
I used for my simulation a model of a diode, obtained through TCAD simulations. So, the device doesn't exist in the technology library, but it has been used to design a rectifier!
Now, I have to draw the layout of the circuit, but I think that if I simply draw the layout of the diode and associate a symbol view, the LVS will not work? A solution that someone suggested to me was to insert a lot of labels in the schematic and in the layout, in order to check that the connectivity is correct! Of corse, the LVS will have the errors due to the unknown devices, but at least the connectivity could be checked.
I hope I was more clear...