It would appear that you may need to add a lot more than 10 to find your "missing" address... from the Wasabi docs:
https://docs.wasabiwallet.io/FAQ/FAQ-UseWasabi.html#what-derivation-paths-does-wasabi-useWHAT DERIVATION PATHS DOES WASABI USE?
Wasabi follows BIP 84: Derivation scheme for P2WPKH Based Accounts, so the main path is m/84'/0'/0'. On TestNet and RegTest Wasabi uses m/84'/0'/0', and not the standard m/84'/1'/0'. Due to the CoinJoin implementation, the key depth can be rather large, thus when recovering the gap limit should be elevated to at least 100.
If o_e_l_e_o's suggestion didn't work... try:
for i in range(0, 100): wallet.create_new_address(True)
If that still doesn't work, then you might also want to try (in case they're using receive addresses as change addresses):
for i in range(0, 100): wallet.create_new_address(False)