Here's a shot of the skinny stock.

Dracaena marginata. Indoor plants have no wind blowing on them, so no cause to form a stronger trunk. The top should take root if you'd like to propagate it. You can stick it in the soil of the existing pot, or in a new pot. The remaining stump should grow one or more new tops to replace it. Might like a bit more light, if possible, but looks healthy and not unhappy.

Also know that D. marginata normally have very slender trunks (not 'stocks'). You should look at as many images as you can so that you can see what they look like under the best of conditions.

Thank you for the responses. This was helpful.

Sorry...thanks for the correction in terminology. Still kind of new at all this. ;-)