I have finally found a good solution. Posting here for the benefit of others.
My code has evolved a bit but basically the key is that I need to call fetch() in order to ensure that the
if(e.view.params.companyID) { varitem = e.view.params.companyID; source.fetch(function() { varitemModel = source.get(item); viewModel.set('currentItem', itemModel); });} else{ varitem = e.view.params.uid; varitemModel = source.getByUid(item); viewModel.set('currentItem', itemModel);}