Also, you should assume you can't rewind time. Any plans you make must commence now, three weeks after the escape.
So it looks like we can't unscrew the pooch then. Damn shame. And that means we lost three precious weeks of potential actions too, ugh.
Keep in mind that you will be playing against competent opponents at the higher levels of hierarchy. These people did not get to the top by being idiots. For example, the first question the Kage who sent you to die will ask is "Where was the battleground, there were chuunin and jounin in that force, there should be scorched earth and exploded trees." followed by "Where are the bodies.", "Do they look like the records we have of our ninja?" and "Why wasn't the enemy force weakened when my force engaged." and leading on to "Did our AWOL force leave a trail that lead towards the enemy at all?". Theoretically you may attempt any plan, of course.
Well, with the skills system, do we even need to explain our actions in order to execute them? Or is it just simply stack as many points into manipulation as you can, cross your fingers, and hope for a nat20? Now if we do need exposition...
We could say that after the commander got brutally assassinated we hightailed it out of there and are on the run from, what we estimate to be, an enemy group of assassination specialists (to explain the lack of destruction from the last three weeks in addition to why we didn't make it to the objective). For those last three weeks we would say we have been sprinting to escape after one of the jonin was killed instantly by an unknown technique while his body was left seemingly untouched. Then we could have some chunin and jonin tear up the landscape we are currently at to fake a battle, maybe contribute some blood to make it more realistic, and send a frantic series of messages describing our rapidly worsening situation. We could say that the enemy used some new technique(s) similar to
The Flying Thunder God Technique (TFTGT) and are actively cleaning up the trail so we would have less of a chance of reinforcements finding us. The last messages we send would say that we are desperately trying to find a way to combat the technique and our speculation on why the enemy takes the bodies from each fight from both factions (because
Edo Tensei has been around since the 2nd Hokage made it). The reason for our former village's ninjas finding our commander's body would be that they wanted our bodies relatively unharmed for some nefarious purpose. Hell, we don't even need to report the correct direction we are now headed (after faking the battle scene, if that step is even necessary); we could send messages irregularly claiming that we suspect the enemy has begun to somehow intercept our messages (ups the spook factor). All we have to do as the PC is tell the jonin our idea and some suggestions on how to make it work. After all, one of them is our sensei. As jonin they know how to report to the Kage and what would make it more believable; that's the beauty of manipulation, using others' strengths to your (occasionally mutual) advantage. I can go into more detail or potential dialogue/messages if need be.
My point is we could spin a tale about some game-changer the enemy has that demands the Kage's attention on the off-chance that we aren't going AWOL and we really do want to complete our mission. TFTGT won a war in canon, and while our PC doesn't know that, a Kage would recognize the significance of such a technique and act defensively. The best case scenario becomes a group of problematic ninjas going missing whereas there is now a possibility this territory dispute could end your village. Does a Kage really want to send out hunter-nin while a war could really start to heat up? At the very least I hope this could buy us some more time.