How do anti-cheats protect against input emulation? - sendinput

Question

There is one game on the Unreal Engine 2 (pirate MMORPG with anti-cheat). I'm using reshade library to hook some functions including dinput/window input handling.
With the SendInput function i can send input but only in the active input field. F1-F12 or 1-9 keys are bind to the panel of skills. I tried to send these keys but nothing happens.
int SendKey(const wchar_t *text)
{
INPUT *keystroke;
UINT i, character_count, keystrokes_to_send, keystrokes_sent;
assert(text != NULL);
//Fill in the array of keystrokes to send.
character_count = wcslen(text);
keystrokes_to_send = character_count * 2;
keystroke = new INPUT[keystrokes_to_send];
for (i = 0; i < character_count; ++i)
{
keystroke[i * 2].type = INPUT_KEYBOARD;
keystroke[i * 2].ki.wVk = 0;
keystroke[i * 2].ki.wScan = text[i];
keystroke[i * 2].ki.dwFlags = KEYEVENTF_UNICODE;
keystroke[i * 2].ki.time = 0;
keystroke[i * 2].ki.dwExtraInfo = GetMessageExtraInfo();
keystroke[i * 2 + 1].type = INPUT_KEYBOARD;
keystroke[i * 2 + 1].ki.wVk = 0;
keystroke[i * 2 + 1].ki.wScan = text[i];
keystroke[i * 2 + 1].ki.dwFlags = KEYEVENTF_UNICODE | KEYEVENTF_KEYUP;
keystroke[i * 2 + 1].ki.time = 0;
keystroke[i * 2 + 1].ki.dwExtraInfo = GetMessageExtraInfo();
}
//Send the keystrokes.
keystrokes_sent = SendInput((UINT)keystrokes_to_send, keystroke, sizeof(*keystroke));
delete[] keystroke;
return 0;
}
Or I can somehow use dinput to send keys?
I know that anti-cheat uses kbdHook (From Kernel-Mode) but how can he keep track of where the keys were sent in the game? (if the active input field works for me)?
PS: If I'm missing something please correct me, thanks!