Custom UITableView headerView disappears after memory warning

I have a UITableViewController. I create a custom headerView for it's tableView in the loadView method like so:

(void)loadView {
    [super loadView];

    UIView* containerView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, width, height * 2 )];  
    containerView.tag = 'cont';
    containerView.autoresizingMask = UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleRightMargin | UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleTopMargin;

    UIButton* button = [UIButton buttonWithType:UIButtonTypeCustom];
    button.frame = CGRectMake(padding, height, width, height);
    ... //configure UIButton and events

    UIImageView* imageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"image.png"] highlightedImage:[UIImage imageNamed:@"highlight.png"]];    
    imageView.frame = CGRectMake(0, 0, width, height );
    ... //configure UIImageView

    [containerView addSubview:button];
    [containerView addSubview:imageView];
    self.tableView.tableHeaderView = containerView;

    [imageView release];
    [containerView release];
}

None of the other methods (viewDidLoad/Unload, etc) are overloaded.

This controller is hosted in a tab. When I switch to another tab and simulate a memory warning, and then come back to this tab, my UITableView is missing my custon header. All the rows/section are visible as I would expect. Putting a BP in the loadView code above, I see it being invoked when I switch back to the tab after the memory warning, and yet I can't actually see the header.

Any ideas about what I'm missing here?

EDIT: This happens on the device and the simulator. On the device, I just let a memory warning occur by opening a bunch of different apps while mine is in the background.