In the last week I have had two separate users asking a similar / related question. In both cases the users stated that data that was in their project had "disappeared". In both cases I followed up, and the data was in fact missing. We discussed how this could be, and I believe that I have tracked it down to the following differences between the way that data is selected when you use different selection methods.
When you do a Select using the drag from lower Left to Top Right or Top Right to Lower Left, or use Polygon Select or Select by Polygon, all of these methods make their data selection from the Graphics Cache - i.e. they can only select data from the view in which you are making the selection and only from data that is visible in the view. Data that is turned off cannot be selected using these methods.
When you do a Select Similar, Select by Layer, Advanced Select, Select by Elevation etc. these are database selections are are carried out regardless of an objects visibility status. This means that you can select objects that are both visible and invisible. And this I believe is what people have done in order to erase data inadvertently from a project.
This is as designed in the product, however I wanted to pose a question to the Users out there as to whether or not you were aware of this difference and also whether or not you feel that this poses a problem or not. We could add a check box to Database type selections that says "Select Hidden Objects" or similar that would maybe be unchecked by default - that would protect Hidden data from these types of searches for example. The main challenge with this of course is that these methods today span all Views and All View Filters whereas adding this checkbox would basically restrict the search to "Currently Active View" and "Currently Active View Filter +/- Selection Set applied"
Since TBC does not have a "Lock Layer" function like AutoCAD, it is hard to have data that is both selectable and protected against deletion. We can make a layer unselectable, but then we cannot even query objects on that layer (because we cannot select them).
Please give us your views on this