Are you sure your employer did it or was it done by the plan's administrator (two different entities). Check with them why and if you can reinvest a portion into the company. Some plans are pretty flexible in that respect.

The employer has the right and is the only one with the right to choose which funds are available for investment. Changes are often made, when they choose to no longer offer a particular fund, they must choose similar options for the participants. Often they get rid of a bunch of affiliated funds. They do have to make a good effort to notify all participants 60 days prior to the change.. mailing notices to all participants to the last known address is sufficient. The letter would have advised which funds were being removed, the last day for you to change them yourself, and what funds they would be moved to if you made no decision. The administrator should have the letter on file, and the date it would have been sent. You cannot go back and change what was done, but you can reinvest as you see fit in the available funds now. Just move what they moved to the fund of your choice. 401k's are nothing like IRA's with multiple funds to choose from, there is always a balanced variety of all types of funds within the 401k plan, but it is completely up to the employer what they choose to offer.

Both employers and 401k administrators are able to alter funds without prior notice. Generally, it's a courtesy move to tell you. You're right to be disappointed that no notification was given. It's standard practice with many businesses to inform you about the changes so you can alter your asset allocation, if desired. If it was done by the 401k administrator, then your employer may not have known.

In any case, it's wise to review your 401k selections immediately after noticing the change. If you're not satisfied with the new funds your money has been placed in, talk to a financial representative from the plan. They should be able to help direct you to more compatible funds. It's very unlikely the 401k has dumped all of the best performing selections in your plan.

Don't just wait until a change occurs to review your 401k. You should take a look at where your money is invested and measure how the fund is performing on a regular basis. Doing a quarterly or even monthly review is sufficient. By taking a more active role in observing your 401k, you may be able to carve out slightly bigger gains or limit your losses by shifting money into funds that are right for you.