Rebuilt transmission will not change gears on the selector

I had a mechanic rebuild my transmission. The guy gives me the car back and now it wont change gears on the selector. Instead of stopping at each letter ( P/R/N/D/D3/D2) It stops at P/R/In between N and D/ In between D and D3. It drives fine like it is supposed to, but now I can physically only go to Reverse, Neutral and Drive. I cant physically move the gear shift to activate D3 because the shift is already at the bottom of the selector console. The mechanic after I brought my car back to him said he already knew about that problem and said it is just the electronics of my gear selector that's bad. I brought it to a family friends mechanic and he said the same thing but he did not look too hard into the situation. My question is, is the gear selector for an automatic 2003 Civic mechanical or electrical? And if it is electrical, how can it physically not sit where it is supposed to and access the wrong gears at the wrong spot?