How do you know for sure what is plugged in?

Question

Computer networks

There is a network for n number of devices. It has several subnets, several vlans. All on ubiquiti. The building has 2 floors, one rack in the server room on the second, there are a couple of switches and the main router, and the second on the first, there are only switches. Patch panels are everywhere, the wires are sewn into the wall.
It is necessary to find where ip phones are physically connected.
Patch panels are only marked at both ends, and both posts on different floors are the same, i.e. conditionally, I have duplicated designations that do not give information where exactly the cable is plugged.
Since there are conditionally two subnets, and two vlans, everything is mixed in them, IP and poppies also do not give anything.
As a matter of fact, I normally see poppies only in IPs issued by dhcp on the router. If I go to the switch itself (managed), then there I don’t see poppies of phones that I know for sure that they are connected there, maybe this is due to the features of the phone’s network card, I don’t know.
If I make a tracer to the phone from the same subnet, it immediately shows the destination, there are no intermediate switches, and here we can actually assume that the computer and the phone are in the same physical switch, and if I see what goes to the switch first, but then it doesn’t go any further , then we can conclude that it is stuck in different equipment. But this assumption, I'm not sure if it's correct, because it also depends on how the vlans are configured.
Perhaps he provided a little too much not particularly necessary information, but only in order to better explain the situation.
Actually tell me how to do it right.

Answer 1

go to the switches one by one and see lldp

If I go to the switch itself (managed), then I don’t see poppy phones there

it doesn't happen.
the switch based on poppies works and all poppies are known to him otherwise nothing would work

Answer 2

If the switch is managed, then it most likely has the ability to view the FDB table. It can be obtained either through the management interface and/or via SNMP. This table has a binding of MAC addresses and switch port.
Here is an article on the topic - https://habr.com/en/post/213247/