This is working fine for me in 4.3.1
I added the original code to cart.php and then modified the template file, except it's not home_main.tpl - the file you need to edit is in skin/modules/Fast_Lane_Checkout/home.tpl
Look for these lines:
Code:
<div class="flc-buttons">
{if !$std_checkout_disabled}
{include file="customer/buttons/button.tpl" button_title=$lng.lbl_checkout style="div_button" href="cart.php?mode=checkout" additional_button_class="flc-3-button"}
{/if}
{include file="customer/buttons/button.tpl" button_title=$lng.lbl_continue_shopping style="div_button" href="`$back_url`" additional_button_class="flc-1-button"}
</div>
<div class="clearing"></div>
and just replace "home.php" with "`$back_url`" - watch the apostrophes