401k Health and welfare benefit

I apologize if this question is not appropriate for this community.

I receive a Health and Welfare Benefit from my employer of $4.50.   If i defer health insurance this is supposed to be deposited into a 401k. After 15 months of employment and checking 401k balances   it's as if there behind almost a year for deposits.

Does anyone know if they can hold on to these deposits?   I do not contribute any extra pay into the acct.

I know they have to deposit my contributions by the 15th of the next month, but that does not apply to me.

I work for a government contractor. All of my correspondence is email and phone.

Any thoughts would be appreciated.

Thanks 

Seb