Terraced mid-terrace house built in 2005 - External cable laid (carport) - Looking for house entry point

Hello, the title might describe the situation somewhat inaccurately.

The problem with our mid-terrace house is that an underground cable was laid to the carport by the electrician back in the shell construction phase (the end looks like it comes out of the ground at the carport). But since we saw no need for it back in 2005 and did not commission it as part of the electrical planning, the electrician (according to his own statement) cut it off/made it unusable.

Now the question arises whether I can still connect it. To my understanding, it was already in the ground, and he would hardly have dug it up to cut it. I guess he trimmed it somewhere on or in the house. My idea would be to find the spot of the house entry and either extend it again from there or lay it from that point to the fuse box. However, I have no idea where the cable might have been laid into the house. In front of the door is a house connection box. In the basement, only the Telekom cable comes out of the wall. Other than that, the wall is "clean" without cables leading into the house. Therefore, I assume that all cables go to the house connection box and enter the house together. Due to the location of the box, it looks like the main cable is led into the house at floor level.

Now my question (I have never dealt with this before): Are the cables in the shell construction practically located in the precast concrete ceiling under the screed? Is that usually done? In electrical installation, does the main cable go directly to the fuse box and get distributed there? Is it likely that an electrician lays the connection cable for the carport parallel to the main cable (if not – as in our case – the cable is not connected at all) and therefore it would no longer be led into the house with the cable? Then I could expose it at the main connection and then extend it anew and introduce it separately into the house.

At the carport, the cable can be energized with a signal, allowing the cable to be traced. It most likely ends at the [Zähleranlage].

The cable at the carport can be energized with a signal, making it possible to trace the cable. It most likely ends at the meter installation.

That’s exactly what I did as well. However, with a "cheap" cable tracer. I connected the signal on one side and grounded it. Unfortunately, no success. Either the radio signal appeared everywhere around the switch box and in the basement (at totally nonsensical spots), or partly not at all anymore.

No cable is visible arriving at the switch box either (I removed the drywall covering to check). All cables arrive except this one 5-core underground cable. Therefore, I suspect it either lies in the main connection box (possibly cut) or was routed with the main cable behind the box into the house. Unfortunately, I can’t see any entry point inside the house, so I believe it must be somewhere under the screed.

The electrician back then can/does not want to remember how and where cables might be laid.