trim comp to work area ruined 3 days of work + a project deadline

Same. I don't understand the reason behind automatically trimming layers when a composition is trimmed.
In result you can't trim say 15 second composition to 5 seconds then to 10 seconds without a need to manually restoring the length of layers.
@Zhby31109485mxs9  check out a free script called: rd_CompSetter
It lets you extend multiple compositions duration length including their layers and precomps.

Trimming comps to the work area does not remove keyframes or animations. It does change layer in and out points, but it does not change the timing. You can open the nested comps (pre-comps) and make them longer again, then adjust the in and out points as needed. If you cut off the front part of the comp, you'll have to lengthen it, select all layers, and move them to the right until the original in points or keyframes can be seen. 

In the future, don't make long comps. Pros don't. After Effects is an animation, compositing, and visual effects app designed to create shots, not edit movies. Edit your movies in Premiere Pro (or the NLE of your choice) just like all the major studios do. Most AE comps should be one shot no longer than a phrase, sentence, or visual idea. Render them, then edit the final movie using the most efficient tool, an NLE.

update: an autosave that randomly happened last night saved me in a sort of way, so check that if you can and lets pray either adobe or someone can make a script or mod that doesnt let that feature trim layers left behind.