How to deal with a senior coworker who sabotaged my work

Question

I currently work on a team being led by a senior coworker with a title equivalent to tech lead in Agile, however I do not report to him. About 3-4 months ago he switched the process from exporting files from our team's repository to directly exporting them from the company software because "the repository did not always have the most up to date files". At the time I was not familiar enough with the software to realize the problems this caused.

Today the company software was down so I exported the files from the old repository (which is still being kept up to date). I realized that the files there are far more up to date than the ones in the system, e.g. version 1 and 2 vs version 6 and 7. I have been doing all the work to update files from early system versions to the current one redoing hundreds of changes that are easily accessible when I only needed to add a couple. I finished 4 tickets today when I had been averaging less than 3 a week.

How can I explain to my manager what has happened here? She thinks that I have been working extremely hard on this project and gave me a gift card for it not long ago. This is further complicated by the fact that she has told other coworkers that he saved the project.

I've lurked enough on this forum to know that you guys likely would recommend polishing the resume after a disaster like this, however I am starting a new position at the same company early next month. I have wasted hundreds of hours of time redoing already completed work and I feel terrible.

Edit1: This is the reason I’m not sure I want to say anything. The situation is confusing and I’ve probably left out important details as to make sure this is not identifiable. I have no concrete proof that he did this purposely, but other people and I have had problems with him in the past. When I first started on the team he was supposed to give us 10 two hour training sessions and he did 3 of them. Management wasn’t concerned either.

Answer 1

How can I explain to my manager what has happened here?

Walk up to Manager and say:

"Hi Mrs Smith. I've just noticed that Version 7 is etc etc. Could be we're duplicating some work. What to do? Can you tell me what you think about this? How to proceed?"

The two relevant communication tips: (1) Never include any meta-language; state facts only. (2) Always finish with a question.

She thinks that I have been working extremely hard on this project [etc]

Totally irrelevant and a non-issue.

This is further complicated by the fact that she has told other coworkers that he saved the project.

There are no complications whatsoever.

All of what you describe is utterly normal in software.

Everything you say is, fortunately, a non-issue.

"It's not high school" - just speak up, then get right back to work.

Regarding the "senior worker". It's unclear what the point is. If you've noticed that version 7 is missing (or - whatever), just open mouth and state "Version 7 is missing". You can say that to both Manager and Senior Worker.

Note that if the manager (or, whoever) is telling you to do something that you feel is silly / wrong architecture / mistaken / etc, in software this is equivalent to noticing that you use a keyboard, or that you're breathing!

It's a total non-issue. The normal situation.

Just (A) do what you're told and (by all means) (B) feel free to simply and clearly state your opinion, while you are doing "A". (C) cash your massive paycheck every payday. Enjoy!