Welcome to the Dell Community @Ian Titor 

When you say "WiFi Hardware missing" 

Do you mean you do not see it in "Device Manager"???

Best regards,

U2

Check the antenna connections to the wifi card.  You may have dislodged or broken them in the repair.

Sorry if it wasn't clear in my post but yes it's missing from the device manager, I also checked the dell bios and saw that it wasn't even getting detected.

I did suspect something related to that might have been the issue, I saw 2 wires connected to the wlan card going up into the screen through the hinges. I brushed it off though because wouldn't that just mean I wouldn't be able to connect, not have the entire card not detected. Also how would I go about testing if they're the issue though, do you mean I'd just use a multimeter and test the wire's continuity?

Its not the Antenna Cables, in that case WIFI card would still get detected in Device Manager and you would have faced only signal issues. 

Unrelated but may be the same case : One time while replacing LCD, the Antenna cable was pulled by me, which Damaged the Card slot of motherboard. 

Only thing you can try to Disconnect Battery Remove Card. Hold the power button down for 30 seconds. Now connect the Card and Battery again,

Reboot to BIOS (F2) > Wireless > Wireless Device Enable : Disable and Enable WIFI > Apply 

Last thing to try  : If you have another working computer, try swapping the card from it. If it's the card than it would be a cheap repair. 

https://www.parts-people.com/index.php?action=item&id=20602

I'll try it but just for clarification, I first disconnect the batter, then remove the wlan card, and then finally hold down the power button for 30 seconds? Will anything happen after 30 seconds pass (for example led will light up then shut off)?

No nothing would happen (visibly) 

Since you have worked on machine internally and that too without a Static Bracelet (LOL, we all do) 

Static charge can cause such issues, 

Remove Battery and WIFI card, hold the power button down for 30 seconds, this will release the static charge from the machine

Now Power on the machine and check if WIFI card is detected. 

If no go, Reboot to BIOS (F2) > Wireless > Wireless Device Enable : Disable and Enable WIFI > Apply 

@Ian Titor 

Exactly why I wanted to make sure if you seen it in "Device Manager"

Loose or unattached cables would not result in it not being present in "Device Manager."

So loose cables is not the solution.

Since Bluetooth is still working does it show in "Device Manager"???

And since you already reseated the card I would say that the WiFi side of the card has failed.

Very unusual as I do not think I have seen this before???

If you look at your driver support page under "Network" you have a few choices of compatible WiFi cards.

https://www.dell.com/support/home/en-us/product-support/product/inspiron-15-5567-laptop/drivers

If you live in the US I can ship you a few to test for free.

Best regards,

U2

Yes bluetooth is still shown in the device manager.

If Bluetooth is getting This means WIFI card is properly seated. Are there any other devices in device manager with yellow marks, or under other devices. 

Have you tried Disabling /Enabling WIFI in BIOS as I had suggested earlier? 

 Reboot to BIOS (F2) > Wireless > Wireless Device Enable : Disable and Enable WIFI > Apply 

Yes, I've tried this. When I disabled both wifi and Bluetooth, the system information in bios says:

wifi device = none

bluetooth device = none

then when I enable both it says:

wifi device = none

bluetooth device = installed

I sent my laptop into Dell for repair of the LCD and when I got it back I had no wifi, so I did what you said and removed the battery cable on the motherboard, holy bananas! All my stuff just reappeared, including my BT adapter which was also missing. THANK YOU! I spent hours doing the bios and even a fresh install of windows like a novice. I can't thank you enough!