Even without the clapper you may be able to find something, like an object set down, or a first word start, that will get you started with sync. Often the hard part is find the corresponding files. Unless they always roll and stop both consistently, the count gets out of sync.
If the timecode was running time of day you MAY be able to find the offset between the 2 for all files. ( a lot of variables there but it’s worth checking.)
On a separate note, I was viewing some Broll material with the producer when we played a source clip and the DP made a comment about the producer. I never got audio on clips after that from that DP. And I’ve been in several edits involving what you are describing. Sorry.
Timecode seems to be a lost art.😀 I hope it works out for you.