It is likely, for whatever reason, that Lr could not find your catelog. It then gives you the option to create a new catelog. If you proceed, then the images imported at that stage will be the only images in a new catelog.
You may have moved the location of your original catelog inadvertently. Do a search on your machine for *.lrcat and see if there are other catelogs on your system. Check the size of the respective catelogs.
If you find your original catelog, if you double click on it it should open in Lightroom. You can then use Import Catelog to import any images (and their current settings) from your recent imports back into your original catelog.