Alex,
It seems you are not using the sap.m.routing.Router, but that should not be the issue I guess...
Please try using one of the following patterns:
Option 1 - use multiple mandatory params without slashes:
{ pattern : "Items/{number}/Types/{ItemType}", name : "Master2", view : "Master2", targetAggregation : "masterPages", targetControl : "idRoot" }
router.navTo("Master2", { number: 0, ItemType: 1 } , false);
Option 2 - pass the context correctly as a query parameter:
{ pattern : "Items:?query:", name : "Master2", view : "Master2", targetAggregation : "masterPages", targetControl : "idRoot" }
router.navTo("Master2", { query : { context : "/Items/0/Types/1" } } , false);
I think I would prefer Option 1, but Option 2 should also be fine...
Cheers,
Nabi